Stonehenge is a large circular structure of huge standing stones surrounded by circular formations dug into the earth. It is located about 13 kilometers (8 miles) north of Salisbury, England. Excavations carried out by London’s Society of Antiquaries since 1919 have assisted current understanding of the site that is supposed to have had three main periods of construction activity. The first period of construction began about 3100 B.C. Native Neolithic people excavated a circular ditch about 98 meters (329 feet) in diameter using antlers for picks. Rubble from the ditch was used to form a high bank within the circular ridge. Two large parallel entry stones were set up. A series of 56 shallow holes (known as Aubrey Holes) was dug and immediately refilled. The site was used for about 500 years before it fell into disrepair.

Stonehenge II brought radical changes, beginning about 2100 B.C. In the center of the site, about 80 bluestone pillars, each weighing up to 4 tons, were erected. These were to form two concentric circles, but were never completed. The stones were brought from the Preseli Mountains, some 385 kilometers (240 miles) distant.

About 2000 B.C, in the initial stage of Stonehenge III, the linteled circle and horseshoe of large sarsen stones were constructed. These remains can still be seen today. The sarsen stones are immense, up to 9 meters (30 feet) in length, and weighing up to 50 tons. They were meticulously smoothed with stone hammers and enclosed a horseshoe formation of five pairs of stone uprights. Each pair of uprights was capped with a lintel stone. During following phases of remodeling, stones were erected and later removed and holes were dug, left to fill with silt.

It is guessed that Stonehenge was used as some kind of religious center but little is really known. The heel stone, probably placed during the second phase of construction, may indicate the site’s use for astronomical purposes. From the center of the circle the sun rises directly above it during the summer solstice. Early people may have been able to forecast eclipses of the sun and moon by relating them to the stone structures. Other experts say that we will never have a clue as to Stonehenge’s significance. Although impressive in size and complexity of construction, Stonehenge is not unique. There are hundreds of similar sites located around Britain.