Avebury Henge is a collection of three large stone circles, larger and older than the more celebrated Stonehenge. The monument is marked by wooden posts at the Avebury site and is, when viewed from the air, in the shape of a pair of glasses, complete with a gap in between the two circles. It's a large set of glasses: together, the two circles cover about 2.5 miles. The posts were close together and would, archaeologists said, have required a large-scale effort of cutting down trees, shaping the posts, digging the holes, and putting the posts in place.

Workers digging in order to install an underground pipeline discovered the wooden circles in 1960s and 1970s; an excavation followed a short time later and turned up evidence of charring, suggesting that the monument had been burned. That 1980s excavation resulted in carbon dating on a shard of pottery found at the site, and the scientists determined at that time that the charring had occurred about 2500 B.C. Current theory suggests that that is roughly the same time as the first stones appeared at Stonehenge.

The archaeologists took advantage of recent advances in carbon dating technology to revisit the Avebury burn site, and the latest results suggest that the site was in use about 3300 B.C.

Pottery shards and animal bones were among the other items found at the dig, along with the remains of some dwellings.

A recent excavation another Neolithic settlement, Durrington Walls, turned up evidence of an ancient barbecue. That site was also home to some of the people who built Stonehenge, according to some historians.

The findings appear in the latest edition of British Archaeology.