The former naval depot at Trecwn is virtually hidden from the outside world in a narrow valley south of Fishguard. It was built at the start of the Second World War as a munitions storage facility and has fifty-eight long storage tunnels dug into the hillsides, all served by a purpose-built railway network. The railway was made of copper to reduce sparks when transporting explosives. A series of interesting bunkers survive in the valley bottom to the north-east at SM 991333 and SM 991335, recorded during RCAHMW aerial reconnaissance.

T. Driver, RCAHMW, 20th March 2009.