There are plenty of reasons to welcome the start of summer. Today, people visiting Stonehenge took that celebration to a whole new level.

The BBC reported that an estimated 10,000 people made the pilgrimage to the 5000-year-old site to partake in summer solstice festivities. "Stonehenge was built to align with the Sun, and to Neolithic people, the skies were arguably as important as the surrounding landscape," Susan Greaney, a senior historian at English Heritage, said in a statement. "At solstice we remember the changing daylight hours, but the changing seasons, the cycles of the Moon, and movements of the Sun are likely to have underpinned many practical spiritual aspects of Neolithic life."

These spiritual aspects are just one of the many fascinating facts about the summer solstice; the day is an extremely old calendar event recognized by ancient cultures across the globe. They include the Druids and other pagans, whose tradition of observing the solstice at Stonehenge has long been upheld by modern revelers.

Scientifically speaking, Stonehenge is an optimal viewing place for the solstice due to its structure. According to TIME, the site’s architects appeared to have kept both the summer and winter solstices in mind during its construction, as the positions of the stones are specifically tuned to complement the sky on both occasions.

The solstices were sacred to the pagans, whose modern-day followers continue to honor their rituals. Pagans in particular refer to the day as Litha, and mark it with activities such as meditation, fire rites, and outdoor yoga.

“What you’re celebrating on a mystical level is that you’re looking at light at its strongest," Frank Somers, a member of the Amesbury and Stonehenge Druids, said in 2014. "It represents things like the triumph of the king, the power of light over darkness, and just life—life at its fullest."

Those who were unable to make the journey can head over to the Stonehenge Skyscape project's website, where English Heritage’s interactive live feed fully captured the experience.