The Llwyn-y-Brain Enclosure is visible as a cropmark that forms a sub-oval, univallate defended enclosure approximately 43m from north to south by 46m from east to west. There are also parchmarks of a fragmentary inner rampart visible on the south side. It occupies a position on a prominent plateau-edge elevated above the valley floor.

T. Driver, RCAHMW, 4 May 2004.