This souterrain was built into the outer rampart of Castle Law fort, close to the entrance, and was excavated by Childe. It has been recovered with a concrete roof to protect it, which at the same time allows you to get a real feel for what a souterrain was like.
The main passage is about 21m in length, running approximately N to S with a curve to the SSW, and widens from around 0.90m at the entrance to around 1.60m at the S end, where there is a slightly rounded terminal. The wall also increases in height from around 1.30m at the entrance to 1.70m at the terminal.
About halfway along the passage there is a low entrance to a round chamber on the W, which measures around 1.60m in diameter and 1.95m in height.
Built into the top of the E wall of the terminal is a cup-marked rock, with approximately five cups (two of which are oval) measuring up to 50mm in diameter and around 12mm deep.
Alternative names for Castle Law