LONDON (AP) — Archaeologists said Monday that they have discovered a major prehistoric monument under the earth near Stonehenge that could shed new light on the origins of the mystical stone circle in southwestern England.

Experts from a group of British universities say the site consists of at least 20 huge shafts, more than 10 meters, or 32 feet, in diameter and 5 meters deep, forming a circle more than 2 kilometers— over a mile — in diameter.

Researchers say the shafts appear to have been dug around 4,500 years ago.

Scientists believe the shafts could mark the boundary of a sacred area or precinct around a circular monument known as the Durrington Walls henge, about 3 kilometers, or 2 miles, from Stonehenge.

The Guardian obtained a photo of the new discovery.