This is a rath, the Irish term for a ringfort, the type of enclosed farmstead that was built across Ireland in the early medieval period, roughly between the fifth and twelfth centuries. Tens of thousands of them survive in various states of preservation, yet each one occupies its landscape in a particular way, and this one at Rockfield has managed to embed itself so thoroughly into the working farm around it that one of its scarps now doubles as a field boundary.

The site is an oval, measuring approximately 22.8 metres north to south and 28.5 metres east to west, which places it in the middle range of ringfort dimensions. To the north and east, the enclosure is defined by a scarp with a broad external slope, while the remainder of the perimeter is formed by a more abrupt, vertical scarp that is partly stone-faced. The interior is level and grassy, with a gentle drop from just east of centre toward the eastern edge. The rise on which it sits gives open views across the surrounding terrain, most extensively to the north and north-east, a quality that would have mattered to whoever chose this spot, whether for watching livestock, monitoring movement across the land, or simply making use of well-drained ground. Sections of the scarp at the east-north-east and north-north-west have been worn down over time by farm stock, a common fate for earthworks that remain in active agricultural use.