Pyramids of Giza Timeline

In 832 AD, the Abbasid caliph al-Ma'mun is said to have tunnelled into the side of the structure and discovered the ascending passage and its connecting chambers. The tunnel was likely used by tomb robbers before being resealed during the Ramesside Restoration, and it was this plug that al-Ma'mun's expedition cleared away.

Another attempt to enter the pyramid in search of treasure is recorded during the vizierate of al-Afdal Shahanshah (1094–1121), but it was abandoned after a member of the party was lost in the passages.

Greaves, in 1646, reported the great difficulty of ascertaining a date for the pyramid's construction based on lacking and conflicting historic sources. Summating the duration of lines of succession, Greaves concluded 1266 BC to be the beginning of Khufu's reign.

Image source: John Greaves

Although seemingly known in antiquity according to Herodotus and later authors, the Descending Passage's existence had been forgotten in the Middle Ages until rediscovery in 1817, when Giovanni Caviglia cleared the rubble blocking it.

Image source: Giovanni Battista Caviglia

In 1837 four additional relieving chambers were found above the King's Chamber after Howard Vyse directed tunnelling to them. The names of Khufu found within these chambers helped make clear that Cheops and Souphis are one and the same.

Image source: Howard Vyse

Today a few of the casing stones from the lowest course can be seen in situ on each side, with the best preserved on the north below the entrances, excavated by Vyse in 1837.

Most notable among modern graffiti is a large, square text of hieroglyphs carved in honor of Frederick William IV, by Karl Richard Lepsius's Prussian expedition to Egypt in 1842.

Image source: Karl Richard Lepsius

Two centuries after Greaves, some of the gaps and uncertainties in Manetho's chronology had been cleared by discoveries such as the King Lists of Turin, Abydos, and Karnak.

Image source: Manetho

Shafts were discovered in the north and south walls of the Queen's Chamber in 1872 by British engineer Waynman Dixon, who believed shafts similar to those in the King's Chamber must also exist. He opened the lower pair of air-shafts, previously closed at both ends, by chiseling holes into the walls.

Image source: Waynman Dixon

In 1874 a mast was installed on the top by the Scottish astronomer David Gill who, while returning from observing a rare Venus transit, was invited to survey Egypt and began by surveying the Great Pyramid.

Image source: David Gill (astronomer)

The first precise measurements of the pyramid were made by Egyptologist Flinders Petrie in 1880–1882, published as The Pyramids and Temples of Gizeh. Petrie noted in 1880 that the four sides of the pyramid were very distinctly hollowed, reasoning this was a result of increased casing thickness in those areas.

Image source: Flinders Petrie

Lazy guides used to block off part of the passage with rubble to avoid leading people down and back up the long shaft, until around 1902 when Covington installed a padlocked iron grill-door to stop this practice.

Nathaniel Davison is credited with the discovery of the lowest of the relieving chambers in 1763, informed by a French merchant named Maynard. In 1909, when the Edgar brothers' surveying activities were encumbered by material in the shaft, they moved the sand and smaller stones back into the shaft, leaving the upper part clear.

Throughout the 20th century the cemeteries next to the pyramid were excavated, revealing extensive information about the people associated with the pyramid complex.

Image source: Giza pyramid complex

In 1936 Hassan uncovered a stela of Amenhotep II near the Great Sphinx of Giza, which implies the two larger pyramids were still attributed to Khufu and Khafre in the New Kingdom.

Image source: Selim Hassan

In 1954 two boat pits, one containing the Khufu ship, were discovered buried at the south foot of the pyramid. The first was discovered in May 1954 by the Egyptian archaeologist Kamal el-Mallakh.

Image source: Khufu ship

A total of 46 samples of the mortar were taken in 1984 and 1995, making sure they were clearly inherent to the original structure. The results were calibrated to 2871–2604 BC, and a reanalysis gave a completion date for the pyramid between 2620 and 2484 BC based on the younger samples.

The second boat pit was examined in 1987; excavation work started in 2010. It was left unopened until 2011 when excavation began on the boat.

A worker's cemetery used at least between Khufu's reign and the end of the Fifth Dynasty was discovered south of the Wall of the Crow by Hawass in 1990.

Image source: Zahi Hawass

The fourth, smaller satellite pyramid (G1-d), is so ruined that its existence was not suspected until the first course of stones and, later, the remains of the capstone were discovered during excavations in 1991–1993.

In 1992, as part of the Upuaut project, a ventilation system was installed in both air shafts of the King's Chamber.

The shafts in the Queen's Chamber were explored in 1993 by the German engineer Rudolf Gantenbrink using a crawler robot he designed, Upuaut 2.

A construction management study conducted in 1999, in association with Mark Lehner and other Egyptologists, estimated that the total project required an average workforce of about 13,200 people and a peak workforce of roughly 40,000.

Image source: Mark Lehner

Mark Lehner discovered a worker's town outside the wall, otherwise known as The Lost City, dated to the reigns of Khafre (2520–2494 BC) and Menkaure (2490–2472 BC). In the early 21st century, Lehner's team also found what appears to have been a thriving port, suggesting the town may have housed soldiers and sailors who used the port rather than pyramid workers.

The National Geographic Society created a similar robot, which, in September 2002, drilled a small hole in the southern door only to find another stone slab behind it.

Research continued in 2011 with the Djedi Project, which used a fibre-optic micro snake camera that could see around corners. They penetrated the first door of the southern shaft through the hole drilled in 2002, and viewed all the sides of the small chamber behind it.

During excavations in 2013, rolls of papyrus called the Diary of Merer were discovered at Wadi al-Jarf, written by a supervisor of the deliveries of limestone from Tura to Giza in the 27th year of Khufu's reign.

Image source: Diary of Merer

In 2016 the ScanPyramids team detected a cavity behind the entrance chevrons using muography, which was confirmed in 2019 to be a corridor at least 5 metres long, running horizontal or sloping upwards.

Image source: ScanPyramids

As to the question of how over two million blocks could have been cut within Khufu's lifetime, stonemason Franck Burgos conducted an archaeological experiment based on an abandoned quarry of Khufu discovered in 2017.

In 2017, scientists from the ScanPyramids project discovered a large cavity above the Grand Gallery using muon radiography, which they called the ScanPyramids Big Void. A team from Kyushu University, Tohoku University, the University of Tokyo and the Chiba Institute of Technology planned to rescan the structure with a newly developed muon detector in 2020.

The mast was damaged in 2019 by a man who evaded security and climbed the pyramid; however, as the mast was periodically changed due to erosion and considered a modern object, the trespasser did not violate Egypt's strict laws regarding antiquities.

After inheritance it was donated to the Museum of Aberdeen in 1946; however, it had broken into pieces and was filed incorrectly. Lost in the vast museum collection, it was only rediscovered in 2020, when it was radiocarbon dated to 3341–3094 BC, over 500 years older than Khufu's chronological age.

In February 2023 the North Face Corridor was explored with an endoscopic camera, revealing a horizontal tunnel with a length of 9 metres and a transverse section of about 2 by 2 metres.

A 3D survey conducted in 2024 revealed previously unknown graffiti within the Great Pyramid.