A broad, roughly circular earthwork sits on a gentle rise in the pastureland of Grangerosnolvan, its most striking feature being the wide, deep fosse, the defensive ditch, that rings the platform. At around 45 metres in diameter, this is a substantial example of a rath, the type of enclosed farmstead that once formed the basic unit of rural settlement across early medieval Ireland. Thousands were built, typically between the sixth and tenth centuries, yet each has its own particular character shaped by whoever raised it and whatever has happened to the ground since.

A survey carried out in 1955 by Danaher recorded a causeway at the south-east of the site, the original point of entry across the fosse, which would have led through a gate into the enclosed living area within. That causeway detail is significant; it is the kind of feature that gives a sense of how the place was actually used, people and livestock moving in and out across a narrow raised crossing. At some point, quarrying cut into the northern edge of the platform, leaving that portion of the monument disturbed and the clean geometry of the original earthwork broken. It is a common enough fate for sites in agricultural landscapes, where the convenience of ready stone or gravel has quietly erased parts of structures that survived centuries of farming otherwise intact.