I FIRST MEET OSMANAGIC on a warm morning in September 2006 at an outdoor café in the center of Visoko. The Sarajevo press has dubbed him the "Bosnian Indiana Jones," an identity he both scoffs at and cultivates. Today, he's wearing a collared white shirt unbuttoned to his navel and a flat-brimmed fedora—just like Harrison Ford's.

Osmanagic pulls out a topo map of the valley and lays it on the table between us. "See, the three largest hills form an equilateral triangle," he says, gesturing with the back of his hand. "And each side is perfectly aligned with east, south, north, and west. Most of the world's major pyramids were built that way."

He starts lecturing me about "geological anomalies." According to a satellite thermal analysis he commissioned in the winter of 2005, the hills lose heat faster than the surrounding topography. He also deployed a ground-penetrating radar device whose images, he thinks, suggest that the Pyramid of the Sun is crisscrossed with passageways that meet at right angles. "Nature cannot make something like that," he says.

Osmanagic drives me to the Pyramid of the Sun in a white Jeep Cherokee emblazoned with the logo of the Bosnian Pyramid of the Sun Foundation, an organization he founded to broadcast the news and collect donations. In the backseat, wearing sunglasses, a safari vest, and beige leather shoes, sits Mohammed Ibrahim Aly, a 53-year-old professor of Egyptology from Cairo who has fallen under the pyramids' spell. I ask Ibrahim Aly why so many scientists claim they're just hills. "It's jealousy," he says. "Or they don't know anything about archaeology. But I'd underline jealousy."

Osmanagic cites small-mindedness from people threatened by the truth. "The trades like geology and archaeology will be the last to accept this, because it's a revolution," he says. "They're afraid." We park at the base of the hill, which has been converted into a sort of boardwalk lined with stands selling T-shirts with images of Osmanagic silhouetted against a backdrop of what appears to be a Maya pyramid. One shirt reads, FUCK THE COUNTRY THAT DOESN'T HAVE ITS OWN PYRAMIDS!

Up on the hill, there are several snack bars and roughly a hundred people milling about, a dozen of them with shovels. The ground is a patchwork of exposed rock and overturned soil. Some areas are roped off. In other places, people traipse right across the exposed megaliths.

We walk uphill for five minutes to a spot where scruffy diggers are scraping away at stone slabs. They put their tools down to gather around a three-foot-deep crack in one of the rocks, where a trio of local construction contractors in blue overalls is getting ready to deploy an industrial endoscope—a semi-rigid hose outfitted with a camera on the tip—that could provide the first look directly inside the pyramid.

"As far as we know it's not a chamber," Osmanagic explains, "but the fact that it is so deep means it must be something."

One guy revs up a portable generator, and the other two snake the camera into the crack. Osmanagic crouches to watch on a small black-and-white monitor. For the first couple of minutes, the screen is a hazy fuzz. And then my heart stops, and I'm pretty sure everyone else's does, too. The hillside erupts in screams of "Semir! Semir!"

Some sort of inscription has come into focus. It's a row of small circles and lines: It looks like writing. Osmanagic snaps a few photos with his camera and then makes a call on his cell phone. An E is clearly visible on the screen, then a D … and then the rest of what I'm pretty sure is the brand name from an old pack of cigarettes. There's a tremor of collective exhalation. Then the camera jiggles and the image is lost.

On the way back to the Jeep, one of the locals shows us a vein of stone running right through the middle of his snack bar. Osmanagic bends over to run his palm across the dirt. It's nothing. "Just a crack," he says.

Once we're out of earshot, Osmanagic says, "Sometimes people see things that don't represent anything. It's OK. We're raising awareness."