Egypt has opened to the public the 4600-year-old "curved" pyramid of King Sneferu.

The 101-meter high structure, located in the royal necropolis of Dahshur, just south of Cairo, is one of two buildings built for Sneferu, the pharaoh who founded the fourth dynasty.

Tourists will be allowed to enter the old structure after archaeologists have discovered "hidden tombs" containing mummies, masks and tools.

The appearance of the pyramid is unusual, with the first 49 meters, which largely retained their smooth limestone mantle, built at a steep angle of 54 degrees before fading to the top.

People can now take a narrow 79m tunnel from an elevated entrance on the north side of the pyramid to reach two rooms in the heart of the old structure.

They may also enter an adjacent 18 m "side pyramid", probably built for Sneferu's wife, Hetepheres, opened for the first time since her excavations in 1956.

While they were opening the pyramids to the public Saturday, archaeologists have shown mummies, masks, tools, and late-period coffins discovered during excavations that began near the Dahshur pyramids. last year.

Mostafa Waziri, Secretary General of the Supreme Council of Egyptian Antiquities, said: "When we took out these objects, we found … A very rich district of hidden tombs."

The pyramid marked a key stage in the evolution of the construction of the pyramid. Its angular shape contrasts with the straight sides of the red Sneferu pyramid, located just north – the first of the fully formed pyramids of ancient Egypt and the next step towards the Great Pyramid of Giza.

The architects changed the angle when cracks began to appear in the structure, according to Waziri.

Mohamed Shiha, director of the Dahshur site, said: "Sneferu lived a very long time … the architects wanted to achieve the complete form, the pyramidal shape.

"Exactly where he was buried, we are not sure. Maybe in this pyramid, who knows.

The authorities seek to promote tourism in Dahshur, located about 17 km south of central Cairo.

The site, which is in the desert, attracts only a net of visitors and is currently free of all-comers from Giza.

The promotion of Dahshur is part of a broader effort to boost tourism, a major source of foreign revenue for Egypt, which fell sharply after the country's uprising in 2011 before gradually recovering.

Archaeologists have also unveiled the nearby tomb of Sa Eset, a supervisor of the Middle Kingdom pyramids, closed since his excavation in 1894 and containing well preserved hieroglyphic funerary texts.

Foreign ambassadors invited to attend archaeological announcements were taken to the narrow spaces of the tomb, which should not be open to the public for two years.

Reuters supplementary reports