Caherlassaleehan is a cashel, a type of early medieval ringfort built from dry-stone walling rather than earthen banks, and at roughly nineteen metres across its interior it falls within the typical range for such enclosures. The wall, where its inner and outer faces still stand, runs to nearly two and a half metres wide, though in places it has slumped into a grass-covered stony mound, and along the southern arc it has been reduced to little more than a low scarp. Brambles have taken over the eastern stretch entirely. Two gaps, each nearly three metres wide, interrupt the circuit at the north-north-west and south-east, likely the original entrance points, though centuries of use and neglect make it difficult to be certain.

The antiquary Thomas Johnson Westropp noted the site by name in 1905 in his survey of monuments within Killaspuglonane parish, which tells us that even by the early twentieth century the cashel was recognised as a named feature of local significance rather than just another field boundary. The site sits on a gentle south-facing rise with open views to the south, while higher ground closes in from the north and east, a position that would have given early occupants reasonable sightlines across the landscape. A small stream running roughly seventy metres to the east marks the boundary of the townland. The interior, sloping gently downward toward the south, is now dense with reeds and offers no visible trace of whatever structures once stood within the walls.