German archaeologist Karl Richard Lepsius discovered the Headless Pyramid in 1842 -- but it was lost beneath the sands of Saqqara, a royal burial site near Cairo.

"After Lepsius the location of the pyramid was lost and the substructure of [the] pyramid never known," said Zahi Hawass, secretary general of Egypt's Supreme Council of Antiquities.

"It was forgotten by people until we began to search this area and a hill of sand, maybe 25 feet {7.6 metres) high."

"Now we are sure that this pyramid is of a style of a pyramid of Dynasty V and belongs to a king called Menkauhor."

"There were missing pyramids of the kings, and this is one of them."

Menkauhor ruled Egypt in the 24th century BC and is the only Fifth Dynasty ruler whose pyramid has not been identified so far.

Archaeologists have not found inscriptions with the name of the pharaoh so far -- the attribution is based on architectural features.

As well as large red granite blocks at the entrance to the burial chamber, the lid of the sarcophagus is made of grey schist -- all characteristic of the Old Kingdom.

"The material of this sarcophagus was never used in the Middle Kingdom," Hawass said.

"The Middle Kingdom pyramids...have complicated corridors until you reach the burial chamber."

"Without discovering any inscription I tell you this is Old Kingdom."

"The substructure is exactly Dynasty V."

Hawass will continue investigating Saqqara -- he believes that the only one third of the site has been fully investigated.

"You never know what secrets the sands of Egypt hide," he said.

"I always believe there will be more pyramids to discover."