Archaeologists have discovered a vast circle of prehistoric pits just a short hop away from the world-famous Stonehenge site in England. Much like the other Neolithic henges in the local vicinity, the newly identified structure is thought to have held some kind of cosmological significance to the prehistoric people who once lived here.

Researchers led by the University of Bradford in the UK revealed evidence for at least 20 prehistoric pits that appear to run in a 2-kilometer-wide (1.2 miles) circle around the Durrington Walls henge, one of Britain’s largest henges – Neolithic banks of earth formed in a circular shape that usually contain a central feature, like a stone or wood monument or pit – found in the Stonehenge World Heritage Site.

The large gaping pits have been noted before but were previously assumed to just be natural features. It wasn’t until archaeologists “zoomed out” on the landscape using geophysical surveys that they noticed the distinct circular pattern and realized they must be human-made. Radiocarbon dating shows the pits, which are over 10 meters (33 feet) in diameter and 5 meters (16 feet) deep, were built 4,500 years ago. Seemingly by no coincidence, this is around the time Durrington Walls, 3 kilometers (1.8 miles) northeast of Stonehenge, was also constructed.

Reported in the journal Internet Archaeology this week, the colossal ring of pits seems to have acted as a boundary to the Durrington Walls henge. Its sheer size suggests that the people who constructed the structure around 2,500 BCE had some grasp of numeracy, which they most likely expressed using a tally system, and perhaps used it for some cosmological function. 

“The pits at Durrington seem to demarcate an area reserved for ritual activity with Durrington walls at its heart. Stonehenge has a similar area defined by burial mounds and it may be that most people did not enter these areas, except for special occasions. There is also a palisade [a defensive wall] on the interior of the circuit,” Professor Vincent Gaffney, lead author and Anniversary Chair in Landscape Archaeology at the University of Bradford, told IFLScience. 

“They really are appearing to deliberately lay out these pits at that space. That says something about their cosmology, but try laying out a line nearly 900 metres without tapes or theodolites," he added. "You have to pace and if you pace over such a long distance then you need to be able to count and have a tally system – that’s a first in Britain.”

Much remains unknown about the structures, but it’s hoped future research in the area could reveal some more invaluable insights into Neolithic Britain along with the vibrant culture that lived near Stonehenge and the Durrington Walls. 

“As the place where the builders of Stonehenge lived and feasted, Durrington Walls is key to unlocking the story of the wider Stonehenge landscape, and this astonishing discovery offers us new insights into the lives and beliefs of our Neolithic ancestors,” Dr Nick Snashall, National Trust archaeologist for the Stonehenge and Avebury World Heritage Site, said in a statement.