History of archaeological exploration

Year 430 BCE: Herodotus, an ancient Greek historian, first mentions the Great Pyramid of Cheops in his first full-length historical work 'Histories’: ‘… but that Kheops, who was the next king, brought the people to utter misery. For first he closed all the temples, so that no one could sacrifice there; and next, he compelled all the Egyptians to work for him. To some, he assigned the task of dragging stones from the quarries in the Arabian mountains to the Nile; and after the stones were ferried across the river in boats, he organized others to receive and drag them to the mountains called Libyan. They worked in gangs of a hundred thousand men, each gang for three months. … The aforesaid ten years went to the building of this road and of the underground chambers in the hill where the pyramids stand; these, the king meant to be burial-places for himself, and surrounded them with water, bringing in a channel from the Nile. The pyramid itself was twenty years in the making. Its base is square, each side eight hundred feet long, and its height is the same; the whole is of stone polished and most exactly fitted; there is no block of less than thirty feet in length. This pyramid was made like stairs, which some call steps and others, tiers. When this, its first form, was completed, the workmen used short wooden logs as levers to raise the rest of the stones; they heaved up the blocks from the ground onto the first tier of steps; when the stone had been raised, it was set on another lever that stood on the first tier, and the lever again used to lift it from this tier to the next. It may be that there was a new lever on each tier of steps, or perhaps there was only one lever, quite portable, which they carried up to each tier in turn; I leave this uncertain, as both possibilities were mentioned. But this is certain, that the upper part of the pyramid was finished off first, then the next below it, and last of all the base and the lowest part. There are writings on the pyramid in Egyptian characters indicating how much was spent on radishes and onions and garlic for the workmen; and I am sure that, when he read me the writing, the interpreter said that sixteen hundred talents of silver had been paid. … The Egyptians said that this Kheops reigned for fifty years; at his death he was succeeded by his brother Khephren, who was in all respects like Kheops’.

Year 60-30 BCE: Diodorus Siculus, an ancient Greek historian, writes the following about the Pyramid in his ‘Bibliotheca Historica’: ‘The eighth king, Chemmis of Memphis, ruled fifty years and constructed the largest of the three pyramids, which are numbered among the seven wonders of the world. … For the largest is in the form of a square and has a base length on each side of seven plethra and a height of over six plethra; it also gradually tapers to the top, where each side is six cubits long. The entire construction is of hard stone, which is difficult to work but lasts for ever; for though no fewer than a thousand years have elapsed, as they say, to our lifetime, or, as some writers have it, more than three thousand four hundred, the stones remain to this day still preserving their original position and the entire structure undecayed. lt is said that the stone was conveyed over a great distance from Arabia and that the construction was effected by means of mounds, since cranes had not yet been invented at that time; and the most remarkable thing in the account is that, though the constructions were on such a great scale and the country round about them consists of nothing but sand, not a trace remains either of any mound or of the dressing of the stones, so that they do not have the appearance of being the slow handiwork of men but look like a sudden creation, as though they had been made by some god and set down bodily in the surrounding sand. … However, there is not a word of truth in this, but the entire material for the mounds, raised as they were by the labour of many hands, was returned by the same means to the place from which it came; for three hundred and sixty thousand men, as they say, were employed on the undertaking, and the whole structure was scarcely completed in twenty years. … And an inscription on the larger pyramid gives the sum of money expended on it, since the writing sets forth that on vegetables and purgatives for the workmen there were paid out over sixteen hundred talents’.

Year 25 BCE: Strabo, a Greek geographer, philosopher and historian who lived in Asia Minor during the transition period from the Roman Republic to the Roman Empire, and the author of the almost entirely preserved ‘Geography’, which is the best source for the study of the geography of the ancient world, visited Egypt, including the Giza Plateau. He reports that the entrance to the Great Pyramid was blocked by a movable stone barrier.

Year 77 CE: Pliny the Elder, a Roman writer, naturalist and polymath, commander of the fleet and army of the early Roman Empire under Emperor Vespasian, author of the encyclopaedic work ‘Naturalis Historia’, which became a model for encyclopaedias, mentions the pyramids of Giza.

Year 820 CE: Al-Ma'mun (Abu al-Abbas Abdallah), son of Harun al-Rashid, seventh Abbasid caliph (813-833 CE), well-educated and with an interest in research, is considered the first to have got inside the Great Pyramid. His men were unable to find a real entrance, but they broke through the stonework in the northern face seven metres above the base of the Pyramid and thus reached the interior of the Pyramid. It is through this passageway that visitors to the Pyramid still enter today. According to Arab historians, when Al-Ma'mun breached into the Pyramid, a big key and some gold coins were found at the end of the tunnel, with their value exactly matching the cost of the operation. Writers at the time told fantastic stories about Al-Ma'mun's work. Analysis of these accounts suggests that the original burial site had already been looted, and the mummies and coffins found there belonged to later burials. It is possible that the passageway actually already existed and had been made by ancient Egyptians who were familiar with the inner arrangement of the Pyramid. It seems they knew the structure inside and bypassed the granite portcullis at the junction of the ascending and descending corridors, and Al-Ma'mun and his men merely widened the passage.

Year 947 CE: Al-Masudi, an Arab historian, geographer and traveller, author of the famous ‘The Meadows of Gold and Mines of Gems’, in which he combines world history with scientific geography, social commentary and biography, spent much of his life adding to and editing his work. He mentions, among other things, the pyramids of the Giza Plateau. Al-Masudi's travels took him to most of the Persian provinces, Armenia, Georgia as well as Arabia, Syria and Egypt.

1100-1165: Al-Idrisi, a Muslim geographer, cartographer and historian who lived for a time in Palermo, Sicily, and wrote numerous works, mentions the Giza pyramids.

1162-1231: Abd al-Latif al-Baghdadi, a physician, philosopher, historian, Arabic grammarian and traveller, and one of the most voluminous writers of his time, mentions the Great Pyramid and notes that the inscriptions on its facing would, if copied, take 10,000 pages.

1364-1442: Al-Maqrizi, a medieval Egyptian Arab historian of the Mamluk era, known for his interest in the Fatimid dynasty and its role in Egyptian history. Most of his works, numbering over 200, are dedicated to Egypt. He also mentions the pyramids of the Giza Plateau.

12th century: the book of “The Thousand and One Nights’, a monument of medieval Arabic and Persian literature, a collection of tales and short stories framed by the story of the Persian king Shahryar and his wife named Scheherazade, mentions how the Caliph Al-Ma'mun got inside the Great Pyramid. The first mention of the Arabic version under the full title ‘Thousand and One Nights’ appears in Cairo in the twelfth century. The Great Pyramid in the tale of Night 398 is mentioned as follows: ’Then, when it was the three hundred and ninety-eighth night, she continued: I have heard, O fortunate king, that in spite of the efforts that the caliph made and the huge amounts of money that he spent in an attempt to destroy the Pyramids, he failed, and all he was able to do was to open up a small hole. It is said that in this hole he found exactly the same amount of money that he had spent, neither more nor less. This astonished him and he took the money and abandoned his intention. There are three Pyramids, and they are among the wonders of the world. There is nothing on the face of the earth so well built, so perfectly designed or so lofty. They have been built with huge rocks, into each side of which the builders drilled holes in which they set up iron bars. They would then drill into a second stone and set it down on the first, filling the space above the bars with molten lead. This was done with engineering exactitude until the whole building was complete. Each Pyramid was a hundred cubits high, using the cubit measure employed at that time, with all four sides sloping from top to bottom over a length of three hundred cubits.’

1546-1549: Pierre Belon, a French traveller, naturalist, writer and diplomat, studied and wrote on a variety of subjects including ichthyology, ornithology, botany, comparative anatomy, architecture and Egyptology. From December 1546 he travelled to Greece, Crete, Asia Minor, Egypt, Arabia and Palestine, and returned to France in 1549. A full account of his observations during this voyage with illustrations was published in Paris in 1553 under the title ‘Les observations de plusieurs singularitez et choses memorables trouvées en Grèce, Asie, Judée, Egypte, Arabie et autres pays estranges’. There is also a reference to the pyramids of the Giza Plateau.

1580-1583: Prospero Alpini, a Venetian doctor, botanist and traveller. To expand his knowledge of exotic plants, he travelled to Egypt in 1580 as doctor to George Emo (or Hemi), Venetian consul in Cairo. Prospero was one of the first Europeans to try and accurately measure the pyramids. Upon return, he mentions in his work on Egypt that the viceroy of Egypt, Ibrahim Pasha, widened the entrance to the Great Pyramid "so that a man could stand tall in it", which actually refers to the passage widened by Al-Ma'mun.

1598-1599: Kryštof Harant of Polžice and Bezdružice, a noble Czech traveller, humanist, soldier, writer and composer known for his expedition to the Middle East. In his book ‘Journey from Bohemia to the Holy Land, by way of Venice and the Sea’ published in 1608, he mentions the pyramids of the Giza Plateau.

1610: George Sandys, an English traveller, visited the pyramids and agreed with the assumption that they were the tombs of kings.

1637: John Greaves, an English scientist, traveller and professor of astronomy at Oxford University, visited Cairo twice, where he explored and took measurements of the pyramids on the Giza Plateau. After his journey, Greaves reported his observations in his book ‘Pyramidographia’. He disagreed with the view that the pyramids had been built by biblical characters or legendary kings. Based on classical sources, Greaves concluded that the pyramids had been built by Cheops, Chephren and Menkaure as tombs. He made one of the first attempts to take detailed measurements of the Great Pyramid using the best tools available at the time and a strict scientific approach. However, the base of the Pyramid was covered in a thick layer of rubble. According to his measurements, the Pyramid's base side length is 693 feet. Greaves climbed the Great Pyramid, measured its blocks and also made his own entrance into the Pyramid. His section view of the Pyramid is remarkably accurate for that time.

1660: Edward Melton, an Anglo-Dutch explorer, mentions the Great Pyramid that he saw in his great journey described in the book ‘Zeldzaame En Gedenkwaardige Zee-En Land-Reizen; Door Egypten, West-Indien, Perzien, Turkyen, Oost-Indien, En D'Aangrenzende Gewesten’.

1692-1708: Benoit de Maillet, a French diplomat, Consul-General in Cairo, traveller and naturalist visited the Pyramid more than 40 times. His sketches show the internal structure of the Pyramid very well, suggesting that the descending corridor was not yet known.

1707-1726: Claude Sicard, a French Jesuit missionary, traveller, explorer and antiquarian, when travelling in Egypt documented twenty major pyramids, twenty-four surviving temples, and over fifty decorated tombs.

1737-1741: Richard Pocock, an English churchman, bishop of Ireland, traveller, visited Egypt and published his notes and sketches in his book ‘Description of the East’. He made a map of the Giza Plateau and schematics of the interior of the Great Pyramid.

1737: Frederick Lewis Norden, a Danish naval captain and traveller, made a journey from as far north as Egypt to Nubia. In his book ‘Voyage d'Egypte et de Nubie’, he mentions the pyramids of the Giza Plateau, including the Great Pyramid. Norden's work stands out for its thoroughness thanks to his occupation as an artist and naval engineer.

1761-1767: Carsten Niebuhr, a German mathematician, cartographer and explorer in the service of Denmark, known for his participation in the Royal Danish Expedition to Arabia, visited Egypt including the Giza pyramids. Carsten assumed that there was another chamber hidden above the King's Chamber, but he was unable to get into it.

1763-1765: Nathaniel Davison, an English diplomat and traveller known for his writings on Egyptian archaeology, travelled to Egypt in the company of Wortley Montague. He documented trips for the Royal Society as a secretary. While exploring the Great Pyramid, Davison discovered a lower relieving chamber above the King’s Chamber and an 'escape shaft'. In 1764, following an echo he heard in the Grand Gallery, Davison crawled 24 feet down the passage from the upper end of the Gallery, full of bat dung, and discovered the chamber that bears his name today. Already then, Davison suggested that the camera had a load-relieving function. He was also able to descend 130 feet down the descending corridor and 155 feet down the ‘escape shaft’ from the Grand Gallery, but he failed to reach the meeting point between the descending corridor and the ‘shaft’ because they were full of rubble and rock debris.

1798: Dominique Vivant Denon, a French artist, writer, diplomat and archaeologist, together with Edme-Francois Jomard, a French cartographer, engineer and archaeologist, and Jean-Marie-Joseph Coutelle, a French engineer, scientist and aeronautical pioneer, created the first topographical map of the Giza Plateau and sketched views of the pyramids as part of Napoleon's large-scale expedition to Egypt. Colonel Coutelle and architectural engineer Jacques-Marie Le Père studied the inside of the Pyramid of Khufu (Cheops) in detail, while Jomard and artist Cecile repeatedly measured the superstructure, including the height of each course of masonry. They also cleared the north-east and north-west corners, revealing two recesses for the Pyramid's cornerstone blocks. Numerous drawings, sketches, maps and descriptions were published a few years after the expedition in a monumental multi-volume publication titled ‘Description de l'Égypte’.

1817: Giovanni Battista Caviglia, an Italian explorer and naval officer, carried out archaeological research upon request of many Europeans visiting Egypt who paid him for the discovered artefacts to add to their collections. Caviglia is believed to have been the first explorer to fully clear the descending corridor and the 'escape shaft', and get inside the subterranean chamber.

1815-1818: Giovanni Battista Belzoni, an Italian traveller and discoverer, was the first to enter the Pyramid of Chephren. He also visited and described the Great Pyramid.

1837: Howard Vyse, a British major, together with John Shae Perring, a British engineer and Egyptologist, were the first to conduct the extensive measurement and exploration of the structure, chambers and surroundings of the Pyramid. Initially, Vyse focused his barbaric explorations with the use of dynamite on the southern side of the Great Pyramid, where he assumed the second entrance was located. However, he was unable to discover anything. Several surviving in situ casing and paving blocks were found on the northern face of the Pyramid. Vyse and his team discovered the so-called relieving chambers above the King's Chamber. He surmised that there was another chamber above Davison's, as he could slip a yard-long reed up through a crack in the north-eastern corner of the chamber. Finally, with the help of dynamite, Vyse found another four relieving chambers within three and a half months. They were named after Vyse’s important friends and colleagues - Wellington, Nelson, Lady Arbuthnot, Campbell. Graffiti was found on the walls of these chambers, left by ancient stonemasons or builders. These hieroglyphic inscriptions are apparently quarry marks made on the stones before they were embedded, except for the horizontal lines on the sides of the Lady Arbuthnot’s Chamber. The explorer of China and Egyptologist Samuel Birch of the British Museum was the first to be able to make notes on the signs and give rough translations of the inscriptions found. Among the inscriptions found is the Khufu’s cartouche as part of the names of the work crews, such as ‘How powerful is the great White Crown of Khnum-Khuf!’. The only case of the king's name as simply 'Khufu', again as part of the working crew's name, is on the south ceiling closer to the west end of the Campbell’s Chamber. As no one has entered it since Khufu's workers sealed it up, the crew names confirm that this Pyramid belonged to Pharaoh Khufu of Dynasty IV.

1842-1843: Karl Richard Lepsius, a German archaeologist and Egyptologist, carried out archaeological excavations of Egyptian pyramids, including the Great Pyramid. Between 1849 and 1856 his monumental twelve-volume work ‘Denkmaeler aus Aegypten und Aethiopien’ was published with many sketches and layout drawings of the pyramids and tombs, including those of the Giza Plateau. Lepsius focused primarily on the structure of the Great Pyramid during his expedition and opined that the core consisted of inclined ascending (accretionary) layers of stonework, and that the size of the Pyramid was determined by the length of time its builder reigned. Other researchers have questioned this statement and the theory is now discredited. Lepsius’s expedition felt it appropriate to mark the birthday of King Frederick William IV of Prussia, the patron of the project, by adding a unique set of hieroglyphic inscriptions to one of the beams of the vault above the original Pyramid entrance. Lepsius recorded the Pyramid in the list of Egyptian pyramids under number IV (4).

1859: John Taylor, an English publisher, essayist and writer, published the popular book ‘The Great Pyramid: Why Was It Built, & Who Built It?’. Taylor, basing his ideas on travellers' records, used a number of mathematical coincidences to claim that the Great Pyramid was built 'to record the measurements of the Earth'. He came to the conclusion that there was a "pyramidal inch", which was 1/25th of the so-called ‘sacred cubit’ and was derived from ancient astronomical observations and measurement of time. Taylor, being a committed Christian, believed that the British inch was thus inspired by God. He argued that the number Pi and the golden ratio may have been deliberately integrated into the design of the Great Pyramid.

1864: Charles Piazzi Smyth, a British astronomer of Italian origin, Royal Astronomer of Scotland from 1846 to 1888 known for his many innovations in astronomy and his metrological studies of the Great Pyramid. Influenced by John Taylor's theories, Smyth travelled to Egypt to take careful measurements of the Pyramid. He subsequently published his book ‘Our Inheritance in the Great Pyramid’, in which he claimed that measurements of the Great Pyramid at Giza suggested 'pyramidal inch’ as a unit of length equivalent to 1.001 British inches, which may have been the measurement standard of the Pyramid builders. Smyth argued that the 'pyramidal inch' was a God-given measure handed down through the ages from the time of Shem, Noah’s son, and that the builders of the Pyramid could only have been guided by the hand of God. In
1874, the Royal Society rejected his paper on the design of the Pyramid of Khufu and Piazzi Smyth resigned in protest.

1872: Waynman Dixon, a British engineer known for his research into the Great Pyramid and the discovery of the only artefacts that were found inside this Pyramid and are now known as the Dixon Relics. Dixon was the first to discover first the southern and then the northern ventilation shafts of the Queen's Chamber, which were originally sealed off. Three ancient artefacts were discovered among the rubble in the shafts - in the southern shaft there was a copper object with a double hook 4.5 cm long with rivets for fastening to wood or bone, and in the northern shaft, a small stone ball about 7 cm in diameter and a piece of cedar wood about 13 cm long. The objects were in excellent condition as they had been sealed hermetically in the shafts for thousands of years. The artefacts were packed in a cigar box and shipped to England. The copper tool and stone ball were donated to the British Museum in 1972 by John Dixon's great-granddaughter, Mrs M. M. Elizabeth Porteous. The piece of cedar was donated to the University of Aberdeen in Scotland in 1946, but only found again by assistant curator Abeer Eladany in 2020 while was conducting an audit of items held in the university's Asian collection.

1874: David Gill, a Scottish astronomer known for measuring astronomical distances, astrophotography and geodesy, together with James Watson, another astronomer from the Detroit Observatory, were involved in research on the pyramids of the Giza Plateau. They installed a steel mast on top of the Great Pyramid, probably to make it easier to measure its height, took precise measurements of the base of the Pyramid by removing all the sand from its cornerstones, and placed bronze geodetic benchmarks in its corners. Petrie, and almost every surveyor have been using Gill and Watson’s benchmarks as reference points ever since.

1880-1882: William Matthew Flinders Petrie, a British Egyptologist, conducted archaeological studies and took accurate measurements of the Giza Plateau focusing primarily on measurements of the Great Pyramid of Cheops. Having become acquainted with Piazzi Smyth’s religious and mystical beliefs, Petrie travelled to Egypt to take more accurate measurements not only of the Great Pyramid, but also of other pyramids and monuments on the Giza Plateau. By accurately triangulating the complex and measuring the pyramids, he identified their true dimensions, thus refuting most of the theories of Piazzi Smyth and John Taylor. Petrie, who has carefully studied the Great Pyramid, also disagreed with K. R.R. Lepsius's ‘accretionary’ theory. He meticulously measured and described every detail, not only from a historical point of view, but also from an architectural and engineering one, as reflected in hundreds of his works. Petrie founded modern Egyptian archaeology, and his thoroughly conducted measurements and research report ‘The Pyramids and Temples of Gizeh’, still remain in the golden pool of fundamental research on the pyramids.

1902-1942: George Andrew Reisner, an American archaeologist who supervised many excavations in Egypt and Sudan, worked with a team from Harvard University and the Boston Museum of Fine Arts on a large-scale excavation of the Giza Plateau complex. Reisner excavated huge fields of mastabas on the eastern, western and southern sides of the Great Pyramid, including its boat pits, and found fragments of gilded wood and pieces of rope in one of them. In 1925, on the eastern side of the Pyramid near satellite pyramid GI-a, Reisner discovered the tomb of Queen Hetepheres, mother of King Khufu, builder of the Great Pyramid.

1903: Ernesto Schiaparelli, an Italian Egyptologist and director of the museum in Turin, excavated the western and eastern sides of the Great Pyramid. Schiaparelli began his excavations on the eastern side of the Pyramid, as he first decided to find out whether Cheops had actually had a funerary temple. He was lucky to discover the remains of the temple, two blocks of which he eventually exhibited in the museum in Turin.

1903-1907: George Steindorff, a German Egyptologist and the head of the University of Leipzig, excavated the western and southern sides of the Great Pyramid.

1909: Morton Edgar and his brother John Edgar, amateur archaeologists, pyramidologists, supporters of the mystical biblical views of Charles Piazzi Smyth and Charles Taze Russell, founder of the religious magazine The Watchtower. The Edgar brothers believed that the dimensions and distances between the inner chambers of the Great Pyramid were precisely related to biblical dates, figures and prophecies, as well as to historical dates. However, regardless of the brothers' beliefs, of particular value are the photographs presented in their work which document the state of the Pyramid before all the restorations, as well as the beautifully produced drawings.

1912-1929: Hermann Junker, a German Egyptologist and the supervisor of excavations from the University of Leipzig, excavated the western and southern sides of the Great Pyramid. In 1912, Junker discovered the huge mastaba G4000, which had been built for Khufu's nephew, Hemiunu, who was responsible for building the Great Pyramid in the early years of the pharaoh's reign.

1916-1921: Émile Baraize, a French Egyptologist who worked almost all his life reconstructing and restoring a large number of ancient Egyptian monuments, including the Great Sphinx and the Great Pyramid. Baraize cleared the area in front of the Pyramid's northern face along with its interior and corridors, which were afterwards repaired and equipped with stairs, ramps and railings to make it easier for visitors to get around.

1925: J. H. Cole, surveyor at the Egyptian Ministry of Finance, took careful measurements of the base of the Great Pyramid at the request of German archaeologist Ludwig Borchardt, the results of which he published as ‘Determination of the Exact Size and Orientation of the Great Pyramid of Giza'. According to his data, the difference between the lengths of the Pyramid's base sides is 10 cm, which differed from Petrie's previously published figures by about half.

1928: Morton Edgar, an amateur archaeologist and pyramidologist, obtained permission from the Egyptian authorities to clear the 'ventilation shafts' of the King’s Chamber inside the Great Pyramid using drill rods. He was also able to investigate the ‘ventilation shafts’ of the Queen’s Chamber, thus determining the length of the southern shaft at the end of which the rod encountered an unknown obstacle. Edgar pointed out that, unlike the shafts in the King's Chamber, the shafts in the Queen's Chamber do not extend to the surface of the Pyramid.

1929-1939: Selim Hassan, an Egyptian archaeologist commissioned by Cairo University and Egyptian Ministry of Antiquities, organised the first expedition on a scale comparable to those of his foreign colleagues. Hassan’s expedition excavated the eastern side of the Great Pyramid, where they managed to clear the ruins of the mortuary temple and the boat pits. He was able to uncover several relief-decorated blocks from the upper end of the causeway. The results of his excavations were published in a ten-volume monumental work ‘Excavations at Giza’.

1932: Ludwig Borchardt, a German Egyptologist, studied the design features of the Great Pyramid focusing on explaining the method used by the ancient builders to measure and orient the site layout plan, and was involved in reconstructing the stages of the Pyramid's construction.

1944: Georges Goyon, a Franco-Egyptian Egyptologist, senior researcher at the National Centre for Scientific Research and King Farouk's private archaeologist, examined the causeway, remains of possible building ramps and blocks of the Great Pyramid's core. Goyon did an enormous and thorough job of documenting the inscriptions and graffiti discovered on the Great Pyramid. The results of this work were published under the title ‘Les inscriptions et graffiti des voyageurs sur la Grande Pyramide’.

1954: Kamal el-Mallakh, an Egyptian archaeologist and inspector of the Supreme Council of Antiquities, discovered two sealed boat pits on the south side of the Great Pyramid that contained intact cedar solar boats. The easternmost of the two boats was removed from the pit and restored to its original form, while the other, western pit remained sealed. The boat was extracted from the pit piece by piece under the direction of Ahmed Youssef, the master restorer who worked on the Hetephaeres funerary furniture. A special museum was built to display the boat on the south side of the Pyramid, where it became available to the public in 1982.

1964: Vito Maragioglio and Celeste Ambrogio Rinaldi, Italian architects, published detailed descriptions and large-scale drawings of the interior and exterior of the Great Pyramid as a follow-up to their two-decade exploration of the Memphis pyramids.

1974: Ain Shams University worked with the Stanford Research Institute (USA) to conduct electromagnetic sounder experiments at the Pyramids of Giza to search for hidden chambers and voids in and around the pyramids. The study was to no avail because the limestone in both of these large pyramids has a high radio frequency loss due to the high moisture content of the limestone.

1979: Joseph Dorner, a German Egyptologist, carried out geodesic measurements of the base of the Great Pyramid for his doctoral thesis, and concluded that the maximum difference between any two sides of the Pyramid was 4.4 cm (almost 1.75 inches).

1984: Hishmat Messiha, an Egyptian archaeologist, carried out the exploration and excavations of the causeway and the valley temple of the Great Pyramid. He determined that the causeway was 660 m long, 18.35m wide with a slope of about 15° to the north at the foot, and that the lower part was built of limestone blocks. Messiha also suggested that the dimensions of the valley temple were 50 m x 50 m. However, he was unable to continue excavating, as the ruins of the temple were right beneath the modern village of Nazlet el-Samman.

1984: Mark Lehner, an American Egyptologist, and David Goodman, a surveyor, carried out a comprehensive geodetic survey of the base of the Pyramid as part of a new project called ‘The Giza Plateau Mapping Project’ to determine the exact length and orientation with respect to the cardinal directions.

1984-1995: the American Research Centre in Egypt (ARCE) funded by the Edgar Cayce Foundation, and the Pyramids Radiocarbon Project supported by its founder David H. Koch collected more than 450 organic samples from monuments built during the Old and Middle Kingdoms to establish their radiocarbon chronology. The analysis of the 46 samples taken from the Pyramid of Cheops suggests that the samples, and presumably the Pyramid itself, are on average 4,147 years old (ranging from 3810 to 5020 years).

1985-1986: Gilles Dormion and Jean-Patrice Goidin, French architects and independent researchers, first carried out a visual architectural survey of the Great Pyramid's interior and later in 1986 the first microgravimetric measurement experiments, together with Électricité de France (EDF), Compagnie de Prospection Géophysique Française (CPGF), the Egyptian Supreme Council of Antiquities headed by Egyptologist Ahmed Qadry, and with financial support from the French Foreign Office. Measurements revealed possible mass anomalies to the west and slightly below the horizontal corridor leading to the Queen's Chamber. Three small holes were then drilled into the western wall of the corridor at the end of the year, but it was found that there were no voids, only irregular masonry and in one place a layer of sand 10 to 40 cm thick. Analysis of the sand showed that it had come from a distant region, possibly Sinai or the vicinity of Aswan. The CPGF team also carried out hundreds of gravimetric measurements and produced an overall density map for the entire Pyramid. Their findings showed that the Pyramid's weight is lower than previously thought, with an average density of about 2050 kg/m³, suggesting that most of the volume consists of local limestone, rubble and probably even some voids filled with sand. The final map of the weight distribution made it possible to see the stepped internal structure of the Pyramid with a small spiral formation.

1987: Sakuji Yoshimura, a Japanese Egyptologist and head of a research team from Waseda University in Tokyo, conducted a microgravimetric and GPR survey of the horizontal corridor leading to the Queen’s Chamber in the Great Pyramid, which revealed a second corridor running parallel to the existing one, but to the west. However, permission was never obtained from the Egyptian authorities for any physical examination of the site. That same year they explored the sealed western boat pit south of the Great Pyramid with a micro camera and confirmed the presence of a second dismantled boat. The pit was then re-sealed until 2008.

1990-1994: AMBRIC, a British-American consortium, and Michael Jones, under the monitoring of Zahi Hawass, an Egyptian archaeologist, were working to improve drainage in the area where the causeway and the valley temple of Cheops had once existed. At six spots they were able to locate the base of the causeway, blocks of basalt paving of the valley temple 4.5 metres below today’s ground level, and the walls of a suspected pier made of limestone and basalt blocks.

1990-1995: Jean Kerisel, a French engineer specialising in soil mechanics and geotechnics, together with Alain Guillon measured humidity, carbon dioxide and air pollution inside the King’s Chamber of the Great Pyramid upon request of the Supreme Council of Antiquities. They found indications that the gas was sinking to the south, precisely in the direction where cracks in the large granite overhead beams of the Chamber could be seen, and suggested installing a mechanical ventilation system. Kerisel returned in 1992 to investigate the Pyramid’s Subterranean Chamber in using ground-penetrating radar (GPR) and microgravimetry. In 1995, he was given permission to drill the rock base of the Subterranean Chamber in search of a cavity, but he was unsuccessful in finding anything.

1991 until now: Zahi Hawass and Mark Lehner, Egyptian and American archaeologists respectively, have been studying the Giza Plateau, including the Great Pyramid under the auspices of Ancient Egypt Research Associates (AERA).

1991-1995: Zahi Hawass, an Egyptian archaeologist and head of the Department of Antiquities, carried out excavations and restoration work on the eastern side of the Great Pyramid on the Giza Plateau. In 1991, his team discovered the base of a previously unknown cult pyramid (GI-d) on the south-eastern side of the Pyramid, and in 1993 they discovered the blocks of its pyramidion, after which the pyramidion was restored.

1992-1993: Rudolf Gantenbrink, a German engineer, and Rainer Stadelmann, an Egyptologist from the German Archaeological Institute (DAI), used specially designed robots with a camera (Upuaut I, Upuaut II) to clear and examine the 'ventilation shafts' of the King’s Chamber, and installed equipment in the northern shaft that would aid air circulation in the chamber. In addition, Gantenbrink was given permission to investigate the orientation of not only the 'ventilation shafts' of the King's Chamber, but also the Queen's Chamber. In 1993, he sent the robot Upuaut II into the southern shaft of the Queen's Chamber. The robot crawled 65 m up the shaft at a 45° angle, where it found a limestone plug with two copper pins sticking out of it. A small shard of copper lay on the floor right in front of it. The northern shaft could not be explored because of the bends and metal rods left by Morton Edgar.

2002: Boston-based iRobot, an American company specialising in the design, manufacture and sale of robotics, supported by National Geographic and the Egyptian Antiquities Service, has developed the Pyramid Rover robot, which was equipped with a track, micro camera and drill, to explore the southern 'ventilation shaft' of the Queen's Chamber. The robot drilled through the previously discovered limestone plug and found a small space that was an extension of the shaft, at the end of which was another plug. The Pyramid Rover was also able to explore the northern shaft of the Queen's Chamber and found the same copper pin plug as in the southern shaft.

2004: Gilles Dormion, a French architect and independent researcher, published the book ‘La chambre de Chéops. Analyse architecturale’ about his research and measurements of the interior of the Great Pyramid of Cheops. In terms of accuracy, quality and description of the Pyramid's elements, the book is one of the best of its kind. In his book, Dormion offers a thorough study of the design features and points out the possibility of a hidden chamber inside the Pyramid.

2006: Clive Ruggles, Emeritus Professor of Archaeoastronomy at the School of Archaeology and Ancient History at the University of Leicester (UK), and Erin Nell measured the orientation of the Great Pyramid and surrounding structures.

2006: Jean-Pierre Houdin, a French architect, published the book ‘Khufu: The Secrets Behind the Building of the Great Pyramid’, in which he outlines the results of over 5 years of research on the Great Pyramid. According to Houdin, the Pyramid was built from the inside out using an internal spiral ramp. Houdin collaborated with Dassault Systemes, a French corporation, in the development of 3D software to simulate his theory.

2008-2011: Sakuji Yoshimura, a Japanese Egyptologist and head of research at Waseda University in Tokyo, and his team re-examined the sealed western boat pit south of the Great Pyramid with a micro camera. Later in 2011, under the direction of Professor Hiromasa Kurokochi, they opened the pit under a dedicated shelter and began to extract and restore the dismantled boat parts.

2010: Dietrich and Rosemarie Klemm, German geologists and Egyptologists, used geochemical and petrographic methods to study about 1500 samples from the pyramids and quarries of the Old Kingdom in order to identify the provenance of the building material of the pyramids. Their research has shown that the main quarry, which was the source of the masonry core of the Pyramid of Khufu, was located about 500 m south of the Pyramid's southern face, and that the casing and backing blocks can be geochemically attributed to the Tura and Maasara limestones.

2011: Robert Richardson, professor at the Public Research University of Leeds in the UK, supported by the Supreme Council of Antiquities, led the development of the Djedi Rover robot, which was equipped with wheels, an echo sounder and a flexible camera to explore more closely the space discovered by the Pyramid Rover robot in the southern shaft of the Queen's Chamber. The robot managed to capture on camera the entire cavity behind the drilled-out plug and found several construction signs painted in red ochre.

2013: Yukinori Kawae, a Japanese Egyptologist, and his team created a 3D model of the cleft at the north-eastern corner of the Great Pyramid.

2013: Pierre Tallet, a French Egyptologist and leader of the excavation team from the Paris-Sorbonne University, discovered the ‘Diary of Merer’ at Wadi al-Jarf on the Red Sea coast. The Diary of Merer is a log-book papyrus written by Merer, an inspector and mid-ranking official, dating back to the 27th year of Pharaoh Khufu's reign during Dynasty IV. The text consists mainly of routine lists of Merer and his team, and the best-preserved sections, Papyrus Jarf A and B, document the shipment by boat of blocks of white limestone from the quarries of Tura to Giza, in order to build the new Pyramid for Pharaoh Khufu - the 'Khufu Horizon'.

2016 up to now: ScanPyramids Project, a scientific mission led by the Supreme Council of Antiquities, initiated, launched and coordinated by the Faculty of Engineering in Cairo and the French institute HIP (Heritage, Innovation and Preservation). Using innovative technologies such as radiographic muons also known as space particles, infrared thermography, photogrammetry, scanning and 3D reconstruction, researchers and three major universities (the Faculty of Engineering of Cairo University, Université Laval of Quebec and Nagoya University of Japan) began their research into the Great Pyramid. In 2017, the mission identified a cavity about 30 m long and 4 m wide above the Grand Gallery and also confirmed the presence of an unknown void behind the vault blocks above the descending corridor, but researchers have not yet been able to open and confirm the presence of these voids. ScanPyramids continues to explore the Great Pyramid to this day.

2018: upon consent of the Egyptian authorities, a photogrammetric survey was carried out by the French company Iconem commissioned by the broadcasting company Label News for a documentary, Pyramids: Solving the Mysteries. The architectural consultant was the French engineer and architect Franck Monnier.