Stonehenge, a prehistoric ruin in southern England, near Salisbury. It is not known who built it, but it is thought to date back to about 2800 B.C. and to have been designed for ritual or ceremonial purposes. Remains of cremated human bodies found buried at Stonehenge indicate that it may have been used as a burial ground. Stonehenge is one of some 80 British prehistoric ruins characterized by a great circular embankment that encloses (or formerly enclosed) some type of structure. Although the original meaning of “henge” is not known, the word is now used for any ruins of this type. At most sites the structures were of wood. Stonehenge, which was built in three phases, contained a wooden structure in its first phase, but was eventually made up completely of stones.

In its final form, Stonehenge had 30 upright stones, each about 18 feet (5.5 m) high and 7 feet (2.1 m) thick, set in an outer ring about 100 feet (30 m) across. Only 17 of these megaliths, called sarsens, are now standing; a few 101/2 foot (3.2-m) lintels still span their tops. Smaller upright stones, called bluestones, form an inner ring. Within it was a horseshoe of five trilithons—two upright sarsens capped by a lintel; three remain standing. At the center was a horseshoe of bluestones around a pillar known as the altar stone.

Outside the sarsen circle is a ring of 56 pits, called Aubrey holes (after John Aubrey, who investigated henge ruins in the 17th century), four small stones, and a circular bank of earth surrounded by a ditch. Two stone pillars flanked an entrance through the earth bank; one remains. An upright megalith, the “heel stone,” is outside the entrance.

To a person standing at the center of Stonehenge on the summer solstice, about June 21, the sun rises from behind the heel stone. In the 1960's some astronomers theorized that the Aubrey holes and some of the stones could be used to keep track of solar and lunar years and to predict lunar eclipses. This led them to believe that Stonehenge was a primitive astronomical observatory. This hypothesis is disputed by some archeologists, who contend that there is no evidence to suggest the builders of Stonehenge had any knowledge of or interest in astronomy.

In its first phase, Stonehenge consisted of only a few stones and wooden posts, enclosed by the circular embankment. It may have been used for religious gatherings.

About 2000 B.C., a people with a more advanced technology brought the bluestones, each weighing about four tons (3,600 kg). They apparently were floated by raft from southwestern Wales. The bluestones were set up to form an inner circle within the embankment. Several centuries later, the sarsens, each weighing about 25 tons (23,000 kg), were brought from as far as 20 miles (32 km) away and set up outside the bluestones. Although tradition connects Stonehenge with the Druids, it is now believed that they had no part in its construction or use.