Ancient Henge ceremonial site near Culbokie. Henges vary in size from just a few metres across to almost 500 metres in diameter at the biggest sites, such as Durrington Walls and Avebury. Even the smallest represent a significant commitment of time and effort by the Neolithic and Bronze-Age communities that built them in the third millennium BC. The largest would have involved hundreds, perhaps thousands, of people in their construction – not only to carry out the actual building work but also to supply the materials, tools, food and other necessities to those engaged in it. Without the advantages of modern technology, and working only with stone tools, antler picks and the like, the henge builders must have been extremely well organised and committed to take on such large and long-term projects. This level of commitment emphasises the importance that must have been placed on henge monuments in antiquity. So what were they used for? Debates rage among archaeologists and others, but the truth is that no one can be entirely sure.