Among the best-preserved ancient villages in South West England, Carn Euny was occupied from the Iron Age until late Roman times. It includes the foundations of stone houses from the 2nd to 4th centuries AD, with walls up to a metre high in places. At the heart of the village is its most intriguing feature – a stone-walled underground passage known as a fogou. This mysterious type of Iron Age monument is found only in the far west of Cornwall. Dogs on leads are welcome.