Sitting on that ridge is a circular earthwork roughly forty metres in diameter, a form of enclosure that would once have defined the boundary of a farmstead or small settlement during the early medieval period in Ireland.

The structure belongs to a class known as a rath, an earthen ringfort built typically between the fifth and twelfth centuries and once so common across the Irish countryside that tens of thousands are thought to have existed. This example at Ballyfintan is defined by two concentric banks with a fosse, or ditch, running between them, the kind of double-banked arrangement that may indicate the site belonged to someone of moderate local standing, since the elaborateness of a rath broadly reflected the status of its occupant. The inner bank remains visible all the way round the circuit, and a gap on the east-northeast side may be where the original entrance once stood. The outer bank has suffered more, with numerous gaps interrupting its line, though it can still be traced from the south-southeast through the west and round to the north-northeast. The fosse between the two banks survives most clearly along the southern and western arc.