For nearly 70 years the locals in Guadalupe, Calif., a hamlet 150 miles north of Los Angeles, have called it "the dune that never moves"—the only one of the towering Nipomo Dunes on the Pacific shore that waves and wind have not managed to shift. Now, documentary filmmaker Peter Brosnan, 38, has unearthed the reason: The sand is anchored by the remnants of the sumptuous set on which movie mogul Cecil B. DeMille shot his 1923 silent epic, The Ten Commandments. (For the 1956 remake, with Charlton Heston and Yul Brynner, the director simply flew the entire cast and crew to Egypt.)

With the loss of some venerable Hollywood sets to a fire at Universal Studios last year, and the replacement of a number of MGM's back-lot backdrops with office buildings, The Ten Commandments site is the last of the larger-than-life film sets. "When we got there," says Brosnan of his first visit, "we saw acres littered with shards of wood and metal and tantalizing chunks of plaster sticking up."

No wonder. DeMille had key parts of the set, including four 20-ton statues of the Pharaoh Ramses, 21 mammoth sphinxes graced with Parton-esque bosoms and 300 chariots, shipped by train from Hollywood to Guadalupe. There, 1,000 workers labored for a month to erect "City of the Pharoahs," whose temple wall towered 110 feet above the dunes. The director shot at Nipomo for one month. He then disbanded his army of 2,500 extras, drawn from the area, and to cut costs simply bulldozed and buried the 10-acre set in a huge trench.

The dunes also served as the Arabian desert in the Rudolf Valentino pictures The Sheik (1921) and Son of the Sheik (1926), and became North Africa in Marlene Dietrich's Morocco (1930). "Valentino became great friends with the local blacksmith, and they'd get roaring drunk together," recalls Guadalupe native Attilio de Gaspere, 77, who wandered the Ten Commandments set as an awestruck extra. "Dietrich refused to walk across the dunes because they tickled her feet. She insisted on riding in her limousine. They finally rigged a sled, put the car on it, and dragged it over the sand."

Brosnan has been seeking the vanished set since 1982, when he was given DeMille's Autobiography, which described the building and burying of City of the Pharaohs. Last fall, Brosnan confirmed the find with ground radar, dug a few test holes, then covered them over to deter looters. He is currently writing grant proposals to raise the $125,000 it will take to rescue and preserve several prime statues.

DeMille would have been amused. He always honored the 11th Commandment: THOU SHALT NOT TAKE SHOWBIZ TOO SERIOUSLY. "If 1,000 years from now, archaeologists happen to dig beneath the sands," the director joked in his autobiography, "I hope that they will not rush into print with the amazing news that Egyptian civilization...extended all the way to the Pacific Coast of North America."