It turns out that a massive prehistoric stone megalith known as the Avebury stone circle is actually a square.

The megalith was built over a period of centuries around 5,000 years ago near the village of Avebury in Wiltshire, UK. The Neolithic monument is one of the biggest stone henges of its kind in the world, measuring 330 meters (1,082 feet) in diameter. It originally consisted of 100 huge standing stones with a central obelisk. Some of the inner stones measure up to 4.8 meters (15.7 feet) high, with the obelisk measuring 6.4 meters (21 feet) in height.

Using a combination of soil resistance surveys and ground-penetrating radar, archaeologists led by the University of Leicester have now discovered “hidden” missing stones, which show that the earliest structures at the site were in the shape of a square (image below).

“Our research has revealed previously unknown megaliths inside the world-famous Avebury stone circle," Dr Mark Gillings, academic director and reader in archaeology in the university's School of Archaeology and Ancient History, said in a statement. "We have detected and mapped a series of prehistoric standing stones that were subsequently hidden and buried, along with the positions of others likely destroyed during the 17th and 18th centuries. Together, these reveal a striking and apparently unique square megalithic monument within the Avebury circles that has the potential to be one of the very earliest structures on this remarkable site.”

This theory of hidden stones has been gaining momentum since the first major excavation of the site by archaeologist and marmalade mogul Alexander Keiller in 1939. He funded this excavation, along with many other archeological projects, using money from his highly successful marmalade business. You know, as you do.

“Our careful program of geophysical survey has finally completed the work begun by Keiller," said Dr Joshua Pollard from the University of Southampton. "It has shown the line of stones he identified was one side of a square of megaliths about 30m across and enclosing the Obelisk."

Pollard added: “Megalithic circles are well known from the time when Avebury was built during the late Neolithic (3rd millennium BC), but square megalithic settings of this scale and complexity are highly unusual.”

Much like its more renowned cousin, the Stonehenge monument, nobody is actually certain why Neolithic people built the Avebury monument. Theories about its original function range from the viable to the downright ludicrous, such as one that says it was built by Native Americans. The researchers from the University of Leicester believe the square megalithic might have commemorated the location of an early Neolithic house from a founding settlement.