Halliggye Fogou is a remarkably well-preserved underground tunnel dating back to the Iron Age. Located on the Trelowarren Estate, on the Lizard Peninsula, the site is believed to date back to the 5th century BC. Little is known about the purpose of these underground chambers; possible uses include storage chambers, hiding places or some kind of shrine. Some sources suggest they could have been used for a combination of all of these.
The word 'fogou' comes from 'ogo', the Cornish for cave, although this isn't a particularly helpful name. Given they date back well over two thousand years they are actually quite remarkable feats of construction. Built by first excavating a trench which would be lined with granite blocks, the tunnel would be finished by placing large flat slabs to form a roof. The whole sites would then be covered with earth creating an almost hidden subterranean space.
Twelve fogous still survive in Cornwall, but along with Carn Euny near Penzance, Halliggye is in a different league. The sheer size and excellent state of preservation are what stand out. From above ground there is little to indicate the site consists of two adjoining tunnels which reach over two metres in height. A straight tunnel stretches away from the entrance steps for around 20 metres, finishing in a narrower section known as a 'creep'. Branching off from this tunnel is an even longer curving section which is 28 metres in length. Originally a further entrance to the fogou was located around halfway along this curved section.
The fogous discovered in Cornwall have all been located within settlements and this is true of Halliggye Fogou. Remains of an Iron Age farming community set within raised earthworks can be found around the fogou itself. These settlements are known as rounds and more than 2,000 dating back to the Iron Age are known about throughout Cornwall.