Carn Euny is an Iron Age settlement on the edge of the West Cornwall moors near Sancreed. There are the remains of several huts dating back to this time but it is the fogou that Carn Euny is best known for.
A fogou is an underground passageway and the one at Carn Euny is over 60 feet (20m) in length. This is the stone chamber off to the side of the main tunnel. Unfortunately at some stage the roof has collapsed so has been replaced with timber. Not sure what the original construction would have been.
All in all it is a pretty impressive piece of work considering it is over 2,000 years old