Excavations 70 yards from the tomb of Tutankhamun in the Valley of the Kings near Luxor are revealing a giant burial complex created 3,300 years ago as a last resting-place for most of the 52 sons and possibly 53 daughters of one of Egypt's greatest rulers, the pharaoh Rameses II.
"This is the most exciting find in the Valley of the Kings since the discovery of Tutankhamun's tomb in 1922," said the foremost expert on Rameses II, Kenneth Kitchen, Professor of Egyptology at Liverpool University.
So far the archaeologists, led by Kent Weeks of Cairo's American University, have discovered in the tomb 48 funerary chapels, 12 entrance chambers and pillared halls, and evidence that several and possibly many more funerary chapels exist. A large area of actual burial chambers survive at a basement level below the chapels.
Rameses is believed by many scholars to have been the pharaoh whose oppressive treatment of the Israelites led to the biblical exodus from Egypt.
Indeed, one of the chambers discovered in the complex has an inscription revealing it was the last resting-place of Rameses' eldest son, Amon Hir Khepeshef (literally, "God Wields His Sword") who, according to the biblical narrative, would have been among those "firstborn of Egypt" said to have been slain by God at the first Passover.
The archaeologists hope to find many more inscriptions in the complex that will help to reconstruct long-lost aspects of of Rameses' 66-year reign.
The mass tomb consists of a 50ft square entrance hall, a T-shaped arrangement of corridors flanked by dozens of funerary chapels - and what appears to be a basement floor almost certainly filled with burial chambers. All the walls were originally covered with painted reliefs depicting the royal princes being presented by Rameses to the gods.
The basement area has not yet been explored, but it is quite likely that the tomb held up to120 children of Rameses.
The pharaoh had plenty of opportunity to procreate during his long reign. He had at least eight major wives - and possibly dozens of minor ones and concubines. He usually kept two senior wives going at a time, replacing them as they died or as he retired them to the harem.
He certainly went in for incest on a grand scale. Dozens of the sons (and possibly daughters) in the tomb were the product of these unorthodox relationships.
The tomb was damaged by flash floods long ago - and, in the 12th century BC, the complex was ransacked by tomb robbers. Indeed, their capture and trial is recorded in a little-known ancient papyrus now kept in a museum in Italy. This 3,000-year-old manuscript was one of the vital clues in locating the tomb.
Strewn over the floors, Professor Weeks's team have found fragments of statues, broken stone vessels, pieces of wooden furniture, thousands of shards of pottery and the bones of cow and bird food offerings.
However, near a sloping ramp leading to the unexplored basement level, the archaeologists also found small fragments of red granite and alabaster sarcophagi (stone coffins), and tiny pieces of mummified humans.
When the archaelogists finally break through into the lower storey, they expect to find utter chaos, with dozens of mummies ripped asunder by ancient thieves searching for treasure. But it should be possible to reconstruct the inscriptions on them and learn at least some of the secrets of Rameses' family.
And, unless the bodies themselves were removed in antiquity, the basement promises to yield the largest single collection of ancient Egyptian royal mummies ever found. The moment of truth will come in around two years' time, when Professor Weeks and his team break into the basement area.
Rameses, who died in 1213 BC at the age of 92, outlived most of his family and was buried less than 50 yards from this mass tomb.
He was a flamboyant and abrasive ruler, and devoutly religious - one of the main objects of his worship being himself. He commissioned several 800-ton sculptures of himself, and seems to have considered himself closer to the gods than most other pharaohs. Although he did not consider himself a true god, he seems to have felt that God's spirit dwelt inside him. And, like other pharaohs, he functioned as an intermediary between God and the people.
Although building temples and tombs was a prime royal activity, it accounted for only an estimated 4 per cent of ancient Egypt's GNP in his reign.
And although many of Rameses' 52 known sons went into the army, and despite several big wars, only around 1 per cent of the economy was accounted for by military spending. About 80 per cent of spending went on agriculture.
The mass tomb was the "big one" which almost got away. In the 1840s, a German egyptologist, Carl Lepsius, stumbled upon the site and thought it was an unfinished royal tomb, the construction of which had been abandoned in favour of a better site. He thought that only the entrance chamber had ever been completed and did not bother to investigate further.
In the 1920s, the entrance was covered up with debris from Howard Carter's excavation of Tutankhamun's tomb, and the site was forgotten.