Legend has it that after filming, it was too expensive to move and too valuable to leave for rival filmmakers to poach—so DeMille had it buried.
In the 1980s, director Peter Brosnan and a group of young filmmakers set out to find the ruins. Over 30 years later, excavations began, and have since turned up a trove of historical artifacts including an entire sphinx broken into pieces. Everyday relics—prohibition liquor bottles, makeup, and tobacco tins—have also been found, shedding light on what life was like for the cast and crew in 1923.
There's also a recent documentary on the subject, titled "The Lost City of Cecil B. DeMille." (Hollywood Reporter)