What remains of the rath, roughly 56 metres in diameter, is enough to read the original intention: a substantial enclosure defined by two concentric banks with a fosse, the term for a defensive ditch, running between them. The outer bank and fosse survive reasonably well along the arc from south-west through north to east, but elsewhere the monument has taken a battering.

Raths were the most common form of enclosed settlement in early medieval Ireland, typically dating from roughly the fifth to the twelfth century, and built to house a farming family along with their livestock and stores. Their earthen banks and ditches conveyed status as much as security. The Tullybeg example was clearly a two-banked example, a form sometimes associated with higher-ranking households, though the damage it has sustained makes any further reading of the site difficult. Quarrying has eaten into the enclosing elements at the south-east, south-west, and north-west, removing sections of bank and fosse that would otherwise have completed the circuit. A trackway, likely a working farm road, cuts across the monument at both the south-east and south-west, compounding the losses. What survives is a partial outline, legible in places and erased in others, the kind of monument that rewards a careful look rather than a quick glance.