Barrow (Ring Barrow), Townparks (Ballyshannon Ed), Co. Donegal

The site is naturally defended by its clifftop position, whilst its landward approach is secured by a substantial earthen bank and a rock-cut fosse, essentially a defensive ditch carved directly into the bedrock. A causeway spans this fosse, marking what was likely the main entrance to the fortification. Within the fort's interior, which is largely level ground, sits a curious horseshoe-shaped mound encircled by its own ditch, positioned just south of the entrance causeway. Faint traces of a low earthen bank can still be detected running along the inner perimeter of the fort.

The most intriguing feature of Dungravenen lies hidden beneath the surface: an elaborate rock-cut souterrain that represents a significant feat of prehistoric engineering. This underground structure, accessible through a southern opening that descends nearly half a metre, consists of multiple interconnected chambers and passages carved from solid rock and roofed with flagstones. The main passage runs north to south for about four metres before opening into a central chamber that stands 1.4 metres high. This hub contains several fascinating details, including a small wall cupboard built into the masonry of the northern wall and a mysterious stone bench or slab in the eastern section, elevated on stone supports.

From this central space, the souterrain branches into additional chambers and passages in multiple directions. To the west, a rock-cut opening leads to another chamber nearly four metres long, whilst to the north, a carefully constructed doorway with a stone lintel provides access to yet another passage. The eastern chamber, now blocked up but visible through a surface opening, extends at least 3.7 metres. With three separate openings to the surface; eastern, northern, and southern; this complex underground system may have served multiple purposes, from storage and refuge to ritual use. The sophistication of its construction, combining rock-cutting techniques with masonry work, speaks to the considerable skill and effort invested in creating this hidden world beneath the promontory fort.