Egyptian antiquities authorities on Thursday made public the discovery of a hidden chamber inside the 4,500 year old Pyramid of Khufu — formerly known as the Pyramid of Cheops — or the Great Pyramid of Giza. The discovery, which was credited to scientists from the ScanPyramids project, was announced by archaeologist Zahi Hawass and Minister of Tourism Ahmed Eissa. ScanPyramids, initiated in 2015, is an international project that uses various high-tech instruments employing non-invasive infrared thermography, ultrasound, 3D simulations and cosmic-ray radiography to study the structures. Scientists say they used that technology to discover a sealed-off corridor above the main entrance to the pyramid. The corridor, which is not accessible from outside the structure, is nine meters (29.5 feet) long and two meters (6.5 feet) wide. After the discovery was made, scientists fed a small diameter (6 millimeter: 1/4 inch) Japanese endoscope through a crack between stones to attain images of the space from inside.