A square formation has been discovered within the Neolithic stone circle at Avebury, a village 130 kilometres west of London. Archaeologists believe the hidden stones, discovered using ground-penetrating radar, were one of the earliest structures at the site, and may have commemorated a Neolithic building dating to around 3500 BCE.
     Previously archaeologists had speculated that the 330 metre diameter outer stone circle - the largest in Europe - preceded its enclosed features. The latest work suggests that a wooden building seeded the monument, a series of stone structures place around it over hundreds of years.
     According to Mark Gillings, an archaeologist at the University of Leicester: "Our working interpretation is that the house is the first thing. It falls into ruin but they're still remembering and respecting it. They put a square around it about 3000 BC and then the circles."
     Clues to the existence of a square structure, each side of which was around 30 metres in length, were first discovered by Alexander Keiller, who excavated in 1939, revealing a number of small standing stones in a line close to the former location of a 6-metre upright stone known as the Obelisk. Keiller's excavation also uncovered postholes and grooves, indicating that a building had once been there, which he supposed was medieval.
     When the newly discovered square was compared with Keiller's notes it was found that the stones were centred on and aligned with the building, suggesting Neolithic origin. Similar Neolithic buildings have been discovered recently at other sites.
     Avebury is a massive monument, largely created during the 3rd millennium BCE. Its perimeter is a 420 metre diameter earthwork, within which is the world's largest known stone circle - a ring of around 100 standing stones which itself encloses two inner stone circles, each constructed around one of two huge megalithic structures known as the Cove and the Obelisk. The Obelisk was recorded in the 18th century as the largest stone at Avebury, but was later destroyed.
     Re-evaluation of records from the 1930s fieldwork revealed a concentration of early and middle Neolithic pottery and worked flint around the Obelisk. Significant was the realisation that the square setting of trenches and postholes are traces of an early Neolithic house in the very centre of the southern inner circle, with the previously known linear arrangement of stones parallel to it proving to be one side of the newly discovered square.
     Radiating from an unusually small standing stone discovered in 1939 south of the Obelisk, are two lines of megaliths extending beyond the investigated area. One cuts through the centre of another circular feature 23.5 metres in diameter, between the southern inner circle and square setting.

Edited from The Guardian (29 June 2017), Arts & Humanities Research Council