Thousands of revelers, new-agers and self-styled Druids descended on the ancient stone circle at Stonehenge, catching a brief glimpse of the sun as they marked the summer solstice — the longest day of the year in the northern hemisphere.

Wiltshire Police say about 23,000 sun-watchers gathered on the Salisbury Plain about 80 miles (130 kilometers) southwest of London on Sunday. Police say the event was peaceful with only nine arrests for drug offenses — fewer than in the past.

Visitors leaned on the stones, dancers swirled on the grass and revelers took selfies as part of the free-form celebrations.

Stonehenge is an icon of Britain, and one of its most popular attractions. It was built in three phases between 3,000 B.C. and 1,600 B.C. and its purpose remains under study.