Archaeologists have discovered a circle of prehistoric shafts located near Stonehenge that is the largest prehistoric monument to be found in the United Kingdom and possibly Europe, according to the New York Times.

The discovery “has completely transformed how we understand this landscape — there is no doubt about it,” Vincent Gaffney, an archeologist from the University of Bradford who was involved in studying the site, told the Times.

The landscape surrounding Stonehenge has been widely studied for years, which is why the sudden discovery of the shafts was surprising to researchers, according to BBC News.

The discovery shows “the capacity and desire of Neolithic communities to record their cosmological belief systems in ways, and at a scale, that we had never previously anticipated,” Gaffney said, according to BBC.

Researchers believe the circle of shafts, which is over 1.2 miles in diameter, was constructed over 4,500 years ago — around the same time as Stonehenge, according to The Guardian. Over 20 shafts have been found so far, and they are each over 16 feet deep and 32 feet in diameter.

“I can’t emphasize enough the effort that would have gone in to digging such large shafts with tools of stone, wood and bone,” said Gaffney, according to The Guardian.

The site is 1.9 miles away from Stonehenge. The prehistoric village Durrington Walls is located directly in the center of the circle, according to The Guardian. Archaeologists believe the shafts were built as a boundary of a sacred site, either to guide people to the site or to warn them away.

“What we’re seeing is two massive monuments with their territories,” Gaffney said, according to The Guardian. “Other archaeologists, including Michael Parker Pearson at University College London, have suggested that, while Stonehenge, with its standing stones, was an area for the dead, Durrington, with its wooden structures, was for the living.”

This discovery comes after the Summer Solstice on Saturday, which is typically celebrated at Stonehenge each year. However, the celebration at Stonehenge this year was canceled due to the COVID-19 pandemic, according to CNN.