As with long barrows, causewayed enclosures can be difficult to spot, but are very easily recognisable from above.
But once you see them, you realise what an incredible feat of engineering they were.
Causewayed enclosures are a series of large concentric ditches, broken by passageways.
They were probably used to gather communities for ceremonies and feasting, as thousands of cattle and sheep bones were found on site.
Building them was also a monumental endeavour, as the only available tools were stone axes and deer antlers.
More than 70 causewayed enclosures have been found across the UK.
Windmill Hill is the largest.
It covers around 20 acres and would have taken around 60,000 hours to build!