VISOKO, Bosnia-Herzegovina -- With eyes trained to recognize pyramids hidden in the hills of El Salvador, Mexico and Peru, Semir Osmanagic has been drawn to the mound overlooking this central Bosnian town.

"It has all the elements: four perfectly shaped slopes pointing toward the cardinal points, a flat top and an entrance complex," he said, gazing at the hill and wondering what lies beneath.

No pyramids are known in Europe, and there is no evidence any ancient civilization there ever attempted to build one.

But Osmanagic, a Bosnian archaeologist who has spent the last 15 years studying the pyramids of Latin America, suspects there is one here in his Balkan homeland.

"We have already dug out stone blocks which I believe are covering the pyramid," he said. "We found a paved entrance plateau and discovered underground tunnels. You don't have to be an expert to realize what this is."

Osmanagic, 45, who now lives in Houston, is personally financing excavations at the Visocica hill, a 2,120-foot hump outside Visoko, a town about 20 miles northwest of the capital, Sarajevo.

He learned about the hill in April from Senad Hodovic, director of a museum devoted to the history of Visoko, which is rich in Bronze Age and medieval artifacts. Hodovic had attended a promotion of an Osmanagic book about ancient civilizations and thought he would like to see Visoko's pyramid-shaped hill.

When the pair climbed the hill, the sweeping view revealed a second, smaller pyramid-shaped hill. It reminded Osmanagic of pairs of pyramids he has seen in Latin America that together create a gateway into a valley.

After obtaining a permit to research the site, which is protected by the state as a national monument, the first probes of the main hill were carried out this summer at six points. Nadja Nukic, a geologist involved in the research, said she found 15 anomalies suggesting that some layers of the hill were manmade.

"We found layers of what we call 'bad concrete,' a definitely unnatural mixture of gravel once used to form blocks with which this hill was covered," Osmanagic said.

"The hill was already there," he added. "Some ancient civilization just shaped it and then coated it with this primitive concrete -- and there you have a pyramid."

Small-scale excavations continued until early November, when winter set in, with the work focusing on what Osmanagic theorizes may have been the entrance to a pyramid-shaped temple.

Anthropologists say the Visoko valley offers ample evidence of organized human settlements dating back 7,000 years. The town was Bosnia's capital during the Middle Ages, and German archaeologists working the valley recently found 24,000 Neolithic artifacts just three feet below the surface.

Osmanagic is taking a cautious approach about the hill.

"No fast conclusions, please. The evidence has to be firm, at least beyond a reasonable doubt," he said.

"Not that I don't believe in a pyramid here," he added. "This place was always called 'Pyramid' by the local population. But we have to prove that this is not a natural shape."

He thinks, however, that the shape of the hill speaks for itself.

"God can make many things, but such perfectly geometrically formed slopes, pointing exactly toward the north, south, east and west -- if he did that, well, that's phenomenal itself."