What makes this particular site worth a second look is the degree to which its structure has survived: two concentric banks with a fosse, or defensive ditch, running between them, and an original entrance causeway still intact on the eastern side.

A rath is an early medieval ringfort, the kind of enclosed farmstead that was the dominant form of rural settlement in Ireland roughly between the fifth and twelfth centuries. Tens of thousands once existed across the country; many have been ploughed flat or built over, which makes the relative preservation here notable. The inner enclosure at Ballagh measures approximately 32 metres north to south and 26.5 metres east to west, defined by an earthen bank and hedge ranging from 4.5 metres wide at the south to 5.8 metres at the north. Beyond that bank lies the fosse, between 5.2 and 6.3 metres wide at the top and up to 0.85 metres deep, and beyond the fosse a second outer bank, which survives along the northern to south-eastern arc and again at the south-west. The entrance, 3.5 metres wide, opens to the east with a causeway crossing the fosse, the standard orientation for ringforts of this type, broadly associated with facing the rising sun. One later intrusion is visible at the southern end, where a field bank running north-east to south-west has been laid across the fosse and outer bank, a reminder that working farmland has a habit of absorbing older boundaries into its own logic over the centuries.