The earthen bank, still standing to around 1.4 metres in height, describes a near-perfect circle of 33 metres across, and has been absorbed so thoroughly into the surrounding field boundary that it is easy to mistake for an ordinary fence line. It is not. A gap two metres wide to the north-north-west hints at where an entrance once stood, and the ground falling away to the south-west and north-north-west preserves the faint ghost of a fosse, the external ditch that once reinforced the bank. Inside, the enclosed area is level and now planted with a mix of pine and deciduous trees.

This is a rath, the earthwork variant of the ringfort, a type of enclosed farmstead built and used throughout early medieval Ireland, broadly from around the fifth to the twelfth centuries. Thousands survive across the country in varying states of preservation, though many have been levelled by agriculture over the centuries. The characteristic form is a roughly circular area defined by one or more earthen banks with corresponding ditches, enclosing a space that would once have contained a dwelling, outbuildings, and perhaps animal pens. At Ballindeenisk, the integration of the ancient bank into a functioning field fence is a common fate for these structures, one that has in some cases helped preserve them by giving farmers a practical reason to leave them standing rather than remove them entirely.