Egypt’s Pyramids of Giza were built to endure an eternity, but how remains one of the ancient world’s greatest mysteries.

The Giza Pyramids, built to endure an eternity, have done just that. The monumental tombs are relics of Egypt's Old Kingdom era and were constructed some 4,500 years ago.

Archaeologists used radar and other methods to find an underground structure near the pyramids and cemeteries in Giza, Egypt.Archive Photos/Getty Images Archaeologists discovered secret structures ...

Researchers look inside a hidden corridor in the Great Pyramid of Giza for the first time in 4,500 years. See what they found ...