The earthwork in Derrymore has been worn so close to the ground that its defining bank has almost been reduced to a scarp, a term for a slope or edge left when a raised feature erodes away to almost nothing. Yet the basic geometry survives: a roughly circular area measuring around 21 metres north to south and 19.5 metres east to west, sitting on a gentle south-south-east-facing slope in improved rough pasture, looking out towards the Cappalaheen River to the south-east.

The site is a rath, the Irish term for a ringfort, a type of enclosed farmstead built across Ireland largely during the early medieval period, roughly between the fifth and twelfth centuries. Thousands once dotted the landscape; many have vanished entirely under plough or development, while others like this one persist in a state of slow dissolution. Here the bank, originally the main defensive and enclosing feature, survives best on the west-south-west to north-west arc, rising to an external height of around half a metre. An outer fosse, a shallow ditch that would have reinforced the bank's enclosing effect, is visible only intermittently and reaches a depth of just 0.2 metres at most. The whole structure is modest by ringfort standards, but its proportions are consistent with a single-family farmstead of the period.

The interior is largely obscured by fallen timber. Mature oak trees line the bank, and large dead boughs and branches have collapsed inward over time, cluttering the enclosed space. An uprooted oak lies across both the centre and the southern section of the bank. The trees themselves are of some interest: oak was long associated with these sites in Irish tradition, and their presence here, whether planted deliberately or self-seeded along the earthwork over centuries, gives the enclosure an atmosphere that bare, cleared ringforts often lack.