Egypt’s antiquities authorities on Thursday unveiled a newly discovered, sealed-off chamber inside one of the Great Pyramids at Giza, just outside of Cairo, that dates back some 4,500 years ago.

The corridor — on the northern side of the Pyramid of Khufu — was discovered using modern scanning technology. It measures 9 meters (nearly 30 feet) in length and is 2 meters (over 6 feet) wide, perched above the main entrance of the pyramid.

Archaeologists do not know what the function was of the chamber, which is not accessible from the outside. In 2017, scientists announced the discovery of another sealed-off corridor, a 30-meter chamber — or about 98 feet — also inside the Pyramid of Khufu.

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Egyptian archaeologist Zahi Hawass and the country’s Minister for Tourism Ahmed Eissa, announced the discovery Thursday at an unveiling ceremony outside the pyramid. The Scan Pyramids project, an international program that uses scans to look at unexplored sections of the ancient structure, was credited for the find.

Scientists from the project — which began in 2015 — attended the unveiling.

Read more: AP