For 75 years, the majestic dunes that tower over this humble coastal village have held one of Hollywood's oldest and strangest secrets.

Cecil B. DeMille, a founding father of motion pictures, once chose this remote, wind-swept site 170 miles north of Los Angeles to erect a plaster replica of ancient Egypt and stage his 1923 silent epic "The Ten Commandments." It had all the right touches, on a monumental scale -- from walls of a pharaoh's city rising 10 stories high to an avenue of nearly two dozen five-ton sphinxes lining the sand. There had never been anything like it, and it remains one of the largest movie sets ever built.

But once the cameras stopped rolling and a cast of thousands was sent packing, it all vanished, for a long time almost without a trace. Then in his memoirs, DeMille dropped a playful hint of the historic set's mysterious fate. "If 1,000 years from now, archaeologists happen to dig beneath the sands of Guadalupe," he wrote, "I hope they will not rush into print with the amazing news that Egyptian civilization, far from being confined to the Valley of the Nile, extended all the way to the Pacific Ocean of North America."

They won't. Because now, in an only-in-California endeavor as sublime as it is ridiculous, what's left of the lost city of DeMille may soon be saved by an authentic archaeological dig like none other.

That all of the Egyptian relics to be excavated are fake hardly matters, at least not to the small and zealous band of filmmakers and archaeologists leading the unusual project, or to the curious towns around here that are beginning to help pay for it. Inside the new Dunes Discovery Center along the creaking and dusty old main street of Guadalupe (pop. 6,000), some worn, fragile DeMille props that already have been discovered are even being displayed reverently in glass cases, as if they were priceless artifacts.

"Digging up a fake Egyptian city in California is hard to do without laughing, I know," said Peter Brosnan, 46, a documentary filmmaker in Los Angeles who has made DeMille's buried set his abiding pastime. "But this is an important piece of early 20th century American history. It's about the only set left from the era of silent film. We know it's down there in the sand, and we think it's mostly intact."

Chunks of artful plaster are not all they are after. The sheer size of DeMille's production also makes it a rich time capsule preserved in a mountain of sand, with abundant emblems of daily life from the 1920s. Something always turns up when the sands shift, such as cough syrup bottles once used to hold sips of alcohol.

To make the film, DeMille marched an army of 2,500 actors from Los Angeles and kept them captive there for two months in an elaborate tent city assembled on the 18-mile stretch of dunes. More than 1,500 construction workers also came to build the mammoth biblical set.

DeMille, who remade the same film in the 1950s in Egypt with Charlton Heston playing Moses, even hired musicians to lug instruments into the sands of Guadalupe and play for the huge cast as it worked. But their performances on the set ended one day when a runaway horse-drawn chariot crashed into the orchestra pit.

"At first I thought that doing a real dig for this was a little strange," said John Parker, a California archaeologist who has worked extensively at the dunes. "In order not to destroy this stuff we have to use the same techniques we would use as if this was a 10,000-year-old prehistoric site. But along with the film history we find, it could be a great way to see what life was like here in the 1920s."

DeMille, who shot the first feature film ever in Hollywood in 1913, undertook the project almost on a whim. His creativity running dry, the legendary director launched a nationwide newspaper contest promising $1,000 to the person who came up with an idea for his next film. Among the 30,000 entries was one from a Michigan man who wrote: "You cannot break the Ten Commandments. They will break you."

He took it as a dare. DeMille wanted to make the silent film in Egypt, but his cost-conscious bosses at Paramount Studios instead shipped him to Guadalupe Dunes, which recently had been the location for another famed silent film, Rudolph Valentino's "The Sheik." It may not have saved them any money.

To create the massive props, which were all adorned with hand-carved hieroglyphics, DeMille hired the designer who inspired the Art Deco movement in architecture. He brought 200 camels from around the country to the set. He paid the Army's top horsemen to drive chariots across the dunes at high speed, and he rented every barn animal for miles around Guadalupe, which is still a farming community.

At one point, a panicked studio executive sent him a telegram from Hollywood saying, "You have lost your mind."

By the time he was finished, DeMille had spent $1.4 million filming the biblical epic, an astonishing sum at the time. And he was way over budget.

Brosnan said that he suspects DeMille buried the set because it was the cheapest option he had. Other film historians contend that he also may have been worried that another director would sneakily use it and release a similar movie faster. No one knows for sure, but answers could lie deep in the sands.

Archaeologists are convinced that more than one-third of the film set is long gone, ravaged by time and the powerful forces of nature along the ocean here. But after using ground-penetrating radar to probe the dunes, some of which slope as high as 500 feet, they believe they finally know exactly where everything that's left has been entombed. Many of the sphinxes, as well as several 35-foot statues of a pharaoh king that DeMille put outside the walls of his phony Egyptian city, seem fairly well preserved, they say.

"They really did a good job hiding it back then," said Liz Scott-Graham, the program manager at the Dunes Discovery Center, a nonprofit group that owns the dunes and treats them like a nature preserve. "You would never know it's all still there."

The site, which is about as large as two football fields, is hard to find. And those who know it well are not at ease revealing the old secret to the few tourists and film buffs who come hunting for it.

Vandals are another fear. But only a few parts of the set have ever reached the surface of the shifting and unspoiled dunes -- splintered scraps of wood and bent wires, clumps of rusty nails, rocks of ornamental plaster so old they fall apart when touched. It hardly looks like treasure, but interest in unearthing it keeps growing.

The campaign to rescue DeMille's lost city has become nearly as epic as the film itself. Brosnan has been working on it for more than a decade in his spare time, recruiting allies, interviewing the few actors from the film who are still alive, and getting tangled in bureaucratic delays.

Ownership of the dunes has changed hands a few times, and there have been debates over what to do with the relics once they are found. The plan now is for Santa Barbara County to split the loot with the Hollywood Heritage Museum.

Archaeologists would like to start the dig next year, but they need to raise about $150,000 more for the meticulous undertaking. It would take months and include injecting the relics with special chemicals to keep them from crumbling when they are dug up.

Nearby towns began contributing to the cause last year, sensing tourist potential. But some potential sources of funding are still worried the project could be too expensive and ultimately pointless.

Even Paramount, the studio that dispatched DeMille to Guadalupe to make "The Ten Commandments," remains skeptical. "There's no guarantee that anything they find buried up there will even be in good condition anymore," one studio official said this week. "It was only plaster."

But Brosnan and his devoted crew have learned to ignore the jokes and doubts about their mission.

"I would love to wait around for another 1,000 years so that everyone would consider this both old and significant," said Parker, the archaeologist. "But the dunes won't let us. The set is slowly but surely disappearing. If we don't do something, a vital part of Hollywood's earliest history will all be gone."