The rath at Mullanashee sits on a ridge above County Sligo, with the ground dropping away to the north and the slopes of the Ox Mountains rising to the south. It is the kind of location chosen with care, commanding a view in several directions, yet what survives today is half-buried in blackthorn bushes and brambles, with loose stone tumbling down the scarp on the south-east and north-east sides.

A rath is a ringfort, the type of enclosed farmstead that was the standard form of rural settlement in early medieval Ireland, typically dating from roughly the fifth to the twelfth centuries. Thousands survive in varying states across the island. This example is roughly circular, measuring around 25 metres on its north-west to south-east axis, and is defined by a scarp, a pronounced slope rather than a freestanding bank, that reaches a maximum height of about two metres on the northern side. Along the south-east to west arc, the scarp carries a low, spread deposit of loose stones roughly four metres wide. Whether this stonework was ever part of the original structure is uncertain; it may instead be the remnant of a later field boundary that was built along or over the rath's edge, reusing the elevated ground as a convenient foundation. The modern field boundary bisecting the interior runs roughly west-north-west to east-south-east, suggesting that at some point the enclosure was simply absorbed into the working agricultural landscape around it, its circular logic overwritten by the straight lines of later land division.