The monument measures roughly 75 metres north to south and 64.5 metres east to west, and is defined by two earthen banks with a fosse, or ditch, running between them. Stone-facing is still visible along the inner bank, a detail that hints at rather more deliberate construction than the surrounding farmland might lead you to expect. What makes the site particularly interesting is a rectangular hollow inside the inner bank at the south-western end, measuring 8.8 metres long and 1.8 metres wide, running east to west and averaging about half a metre in depth. Stones protrude from its sides, and a large stone sits near its midpoint. This is thought to be a possible souterrain, an underground or semi-underground passage typically associated with early medieval ringforts, where they served as storage spaces, refuges, or escape routes.

Ringforts of this kind were the primary form of rural settlement in early medieval Ireland, probably built and occupied between roughly the fifth and twelfth centuries, and thousands survive across the country in varying states of preservation. The Caltra example is in fair condition, though not intact throughout. The fosse and outer bank have been lost between the east-north-east and south-south-east arcs, and a later field wall has been built directly over the outer bank to the west and from north to north-north-east, the kind of quiet overwriting that happened across centuries of agricultural use. The townland boundary itself cuts through the monument at the north-west and east. Within the south-western interior, there are also traces of an internal subdivision, suggesting the enclosed space may once have been organised into distinct functional areas. To the north of where the boundary crosses the monument lies a cashel, or stone-built enclosure, a separate but related monument type recorded nearby.