The waterlogged terrain would have made any direct approach difficult, and yet whoever settled here could see clearly for long distances down the valley to the south-west, a classic trade-off between discomfort and defensibility that recurs throughout medieval Irish settlement.

An earthen bawn, the term for a defensive enclosure, typically walled or embanked, used to protect livestock and buildings around a tower house or fortified residence, encloses the remains. Within its interior, the foundations of several structures survive in the southern quadrant, tracing along both the south-east and south-west sides of the enclosure. The walls stand only around half a metre in height and average roughly 0.7 metres in width, but their outlines are legible enough to suggest a small settlement rather than a single building. One of these structures has roughly square proportions and larger dimensions than the others, and it is likely the remains of Castle Warren itself, a site already marked on the first edition six-inch Ordnance Survey map of 1839. A smaller building foundation also survives within the western angle of the bawn, separate from the main southern grouping. The site has a surface water supply, which would have been essential given the isolation the marshy ground imposed.