For the first time since 1965, Egypt has opened the Bent Pyramid — which was built for Pharaoh Sneferu — to visitors as part of a bid to lure tourists from the Great Pyramid of Giza.

Key points: The 4,600-year-old pyramid was built during the Fourth Dynasty

The 4,600-year-old pyramid was built during the Fourth Dynasty It is one of Egypt's oldest structures and is a precursor to the Great Pyramid of Giza

It is one of Egypt's oldest structures and is a precursor to the Great Pyramid of Giza Authorities are hoping the reopening will help to boost tourism at the world-heritage site

Tourists will now be able to clamber down a narrow 79-metre tunnel from a raised entrance on the pyramid's northern face to reach two chambers deep inside the 4,600-year-old structure.

The 101-metre structure just south of Cairo marks a key step in the evolution of pyramid construction between step pyramids and complete pyramids.

They will also be able to enter an adjoining 18-metre-high "side pyramid", possibly built for Sneferu's wife Hetepheres, which was opened for the first time since its excavation in 1956.

The Bent Pyramid is one of two built for Fourth Dynasty founding pharaoh Sneferu in Dahshur, at the southern end of the Memphis necropolis that starts at Giza, a UNESCO World Heritage Site.

A member of an international delegation sketches the site of the Bent Pyramid during its reopening. ( AP: Maya Alleruzzo )

The pyramid's appearance is unusual, with the lower section built at a steep angle which then tapers off higher up — giving the structure its "bent" appearance.

The promotion of Dahshur is part of a wider push to boost tourism, an important source of foreign revenue for Egypt that dipped steeply after the country's 2011 uprising, before gradually recovering.

The angular shape contrasts with the straight sides of Sneferu's Red Pyramid just to the north, the first of ancient Egypt's fully formed pyramids and the next step toward the Great Pyramid of Giza.

Architects changed the angle when cracks started appearing in the structure, said Mostafa Waziri, secretary-general of Egypt's Supreme Council of Antiquities.

Mohamed Shiha, director of the Dahshur site, said the original ambition was for a traditional pyramid design.

"Sneferu lived a very long time, the architects wanted to reach the complete shape, the pyramid shape," he said.

"Exactly where he was buried — we are not sure of that. Maybe in this [Bent] Pyramid, who knows?"

Women look at recently discovered artefacts found at the Bent Pyramid site. ( AP: Maya Alleruzzo )

Authorities are seeking to promote tourism at Dahshur, about 28 kilometres south of central Cairo, which lies in the open desert and attracts just a trickle of visitors.

It is largely free of the tourists and bustle found at Giza.

As they opened the pyramids, archaeologists also presented late-period mummies, masks, tools and coffins discovered during excavations that began near the Dahshur pyramids last year and are due to continue.

"When we were taking those objects out, we found a very rich area of hidden tombs," Mr Waziri said.

Archaeologists also unveiled the nearby tomb of Sa Eset, a supervisor of pyramids in the Middle Kingdom, which has been closed since its excavation in 1894 and contains finely preserved hieroglyphic funerary texts.

Foreign ambassadors invited to attend the archaeological announcements were led, sweating, into the tight spaces of the tomb.

It is not expected to be opened to the public for another two years.

ABC/wires