They could have been cremation pits, cock-fighting rings, animal pens, Civil War foxholes or secret hiding places for moonshine equipment.

Maybe they were prehistoric Indian burial sites, charcoal pits or foundations for native American abodes. Or maybe, some say, the stone circles dotting the western slope of Polish Mountain encircled apple trees in the early 1900s.For more than a decade, 150 to 200 circles of sandstone rock have puzzled area residents and archaelogists. Virtually hidden by brush and poison ivy, the gray-colored rocks of various shapes and sizes are neatly arranged in circles.

No one knows their purpose, or who put them there.

"Everybody that goes up there has some kind of weird theory," said John Mash, manager of Green Ridge State Forest, where the circles are found. "One guy even mentioned that they could have been sweat lodges - like a Turkish bath.

"The Indians would have these rituals when they would go into manhood," he said. "They would go in these buildings with hot rocks and put water on them - something like a sauna."

But 150 to 200 saunas on one hillside in western Maryland?

Mash said rangers noticed the stone rings in the early 1970s. In 1975, Mash contacted State Archaeologist Tyler J. Bastian, who visited the site and put the circles on a list of archaeological areas in Maryland.

But it was not until last year that some archaeologists and volunteers excavated one of the circles. "They did the dig and found zip, except for the rattlesnakes," Mash said.

Hoping to uncover clues, another group conducted a dig this spring.

"In a nutshell, we didn't discover anything. They still remain a mystery," said Charles McVeigh Jr., a member of the Western Maryland Archaeological Society.

No future digs are planned, and meanwhile, the state forest has put the circles on its historic preservation list to ensure the five-acre tract remains untouched, Mash said.