The celebrations haven't always been so welcoming. Violent clashes between police and revelers in 1985 forced English Heritage, who manages and maintains Stonehenge, to close it to the public. English Heritage reopened it to celebrations in 2000, and the event has remained largely peaceful, although arrests were made this year.
This celebration, carried out today with bonfires, dances and courtship rituals, is a modern twist on solstice celebrations, or the coming of summer, which were once a traditional holiday on the pre-Christian calendar.
Solstice celebrations are tied with agriculture and mark a key turning point in the growing season. They date back to the time of the ancient Egyptians -- the Great Pyramids were specifically placed so that the solstice sunset could be easily viewed from the Sphinx -- and continue to be recognized by many cultures around the world today.