A reveler prays at sunrise as thousands gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)

STONEHENGE, England (AP) — Dancers, musicians and revelers have watched the sun flicker over the horizon at Stonehenge, celebrating the summer solstice at the Neolithic stone circle.

The sun rose behind the Heel Stone, which traditionally marks the spot on the horizon for the sunrise, at 4:52 a.m. Friday (0352 GMT; 11:52 p.m. EDT Thursday). The rays streamed through the circle, marking the longest day of the year in the Northern Hemisphere.

Wiltshire Police estimated that 10,000 people attended. There were four arrests at Stonehenge and another at the nearby ancient monument in Avebury.

Stonehenge, a World Heritage site, is believed to be 4,500 years old. It is known for its alignment with the movements of the sun.

Revelers meditate next to stones at sunrise as thousands gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
The sun rises as thousands of revelers gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
Revelers perform at sunrise as thousands gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
Revelers stand next to stones at sunrise as thousands gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
A reveler meditates between stones at sunrise as thousands gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
A reveler performs at sunrise as thousands gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
The sun rises as thousands of revelers gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
The sun rises as thousands of revelers gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
Revelers rest on a stone at sunrise as thousands gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
Revelers perform yoga soon after sun rise at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
The sun rises as thousands of revelers gather at the ancient stone circle Stonehenge to celebrate the Summer Solstice, the longest day of the year, near Salisbury, England, Friday, June 21, 2019. (AP Photo/Aijaz Rahi)
People turn to face the rising sun at Stonehenge as crowds of people gather to celebrate the dawn of the longest day in the UK, in Wiltshire, England, Friday June 21, 2019. (Ben Birchall/PA via AP)
People offer salutations to the sun, at Stonehenge as crowds of people gather to celebrate the dawn of the longest day in the UK, in Wiltshire, England, Friday June 21, 2019. (Ben Birchall/PA via AP)
A woman performs a handstand between stones at Stonehenge as crowds of people gather to celebrate the dawn of the longest day in the UK, in Wiltshire, England, Friday June 21, 2019. (Ben Birchall/PA via AP)
A man is bathed in the rising sun inside the stone circle at Stonehenge as crowds of people gather to celebrate the dawn of the longest day in the UK, in Wiltshire, England, Friday June 21, 2019. (Ben Birchall/PA via AP)
The sun rises between the stones at Stonehenge as crowds of people gather to celebrate the dawn of the longest day in the UK, in Wiltshire, England, Friday June 21, 2019. (Ben Birchall/PA via AP)