traces of human activity in carn euny have been detected from the early neolithic period. the first settlement of wooden huts was around 200 bc. in the 1st century bc these were replaced by stone huts, the remains of which are still visible. at this time, the people of carn euny lived from agriculture, livestock, trade, and perhaps tin mining. the houses were of a type with enclosed courtyards. the most important structure of the site is certainly the fogou (cornish for "cave"), a man-made underground passage which is covered with massive stone slabs. fogous can be found in other places in the uk and ireland, and are known more generally as souterrains. their purpose is unclear. the fogou of carn euny is in particularly good condition and consists of a 20 m long corridor, with a side passage that leads to a round stone chamber with a collapsed roof, and a small tunnel which may be a second entrance.