Primal power symbol, Stone Age observatory or Druid sacrifical altar, Stonehenge has come to mean many things to different ears.

Indeed, to some people - like the hippies who gathered for the summer solstice a few weeks ago - the stones represent a way of life. To them, the giant ring epitomizes a lost era of ecological harmony from which the world has sadly wandered.Unfortunately, the facts do not support this notion. Nor do they fit any other theory for that matter. Despite advances in archaeology, the great structure steadfastly refuses to fall into simple categories.

"Stonehenge was built on a vast scale," says archaeologist Julian Richards. "It was in use for more than 2,000 years. I don't think it could only have had one purpose for all that time. Its function evolved with changing needs."

Richards recently completed an intriguing survey of Stone Age dwellings in the area, work that involved much tramping over ploughed fields in winter months (when crops do not hide stones, flints and other artifacts) in search of ancient settlements.

The results were surprising. It was previously thought Stonehenge lay in the middle of a vast, lonely ritual landscape, surrounded by burial mounds, called barrows, and other monuments, many as grand as Stonehenge itself.

In fact, the area appears to have been a hive of activity peppered with settlements, fields and flint factories.

"Far from being a remote, terrible place ruled by priests, Stonehenge was part of the fabric of everyday life," said Richards.

Archaeologists trace Stonehenge's birth to 4,000 B.C. with the arrival in Britain - which was then thickly wooded from coast to coast - of the first farmers from Europe.

As one of their first acts, these people probably created a circle or clearing for religious celebration. Later, as the rest of the landscape was similarly stripped of vegetation, the circle was marked by wooden posts and finally stones. The result was Stonehenge.

Victorians thought humans were sacrificed, while more recent theories have suggested that Stonehenge was used as a giant astronomical observatory.

Certainly, Stonehenge is aligned to celestial configurations. But that doesn't mean it was built specifically to study the stars, says Cambridge archaeologist Christopher Chippendale, author of "Stonehenge Complete."

"Stonehenge was not a prehistoric observatory, or a machine for studying the sky, but at most was a monumental commemoration in stone of something long since discovered and perhaps already on its way to being forgotten," Chippendale wrote.