It is thought that the stones of the Cove were the first stones erected inside Avebury’s circle. There were originally three stones, arranged to form an open-topped, three sided structure. Aubrey Burl explains in ‘Prehistoric Avebury’ how coves are ‘monumental versions of tomb forecourts and entrances’ – which makes sense when you think of Lugbury, which is quite local. When the cove was built the chambered tombs were no longer being used. It’s possible that bones of ancestors were brought to the cove instead as part of rites there. About a dozen coves are known countrywide, which are similarly upstanding and are open in one direction, usually the east. Avebury cove faces NE, towards the fairly bland skyline of Hackpen Hill, perhaps symbolically facing the general direction of the midsummer sunrise?
The third, northernmost stone of the Avebury cove fell in 1713. The other two were becoming more wobbly and have recently been made safe, as you can read about on Pete and Alison Glastonbury’s website. Their hugeness surprised the archaeologists, as you can see here: themodernantiquarian.com/post/13206
As Burl says, such enormous stones must have been carefully searched for, required huge effort to transport, and in fact they required sarsen blocks and cobbles in their trenches to provide extra support for their huge weight. Because of their size they had to be set reasonably far apart, to leave enough room to lift and position them.
Stukeley reported that “The vulgar call them the devil’s brand-irons from their extravagent bulk, and chimney-like form”