A promontory fort uses natural terrain, typically a headland or cliff edge, as part of its defences, with artificial banks and ditches cutting across the accessible neck of land to complete the enclosure. Here, the natural feature is not a coastal cliff but the steep confluence of two rivers: the Awbeg and the Bregoge meet just below this roughly rectangular tongue of elevated ground, approximately 80 metres from north to south and 60 metres from east to west. The rivers do the work on three sides, dropping sharply to the valley floor. Aerial photography taken in 1998 revealed two levelled banks crossing the neck of the promontory, and a ground inspection confirmed them as low, grass-covered undulations running across the golf course fairway, easy to walk over without noticing.

The site sits immediately south of the Old Court graveyard and carries considerable, if contested, historical weight. Writing in 1902, a scholar named Jones identified this as the location of Dún ar aill, the fort from which the town of Doneraile takes its name. A 1937 Ordnance Survey six-inch map, following Jones, labels the ground as the "Old Town of Doneraile (site of)", though the map symbol was placed slightly too far to the east. Jones also recorded a tradition that in 1130 a family of the clan known as Deena or Deagha built their forts on this site, though he provided no source for that date, and it should be read cautiously. A separate scholar, Power, writing in 1932, placed the original name-giving fort not here but at the site of a later castle nearby, which only deepens the uncertainty about where exactly the earliest settlement began. The golf course has landscaped and cleared the eastern slope, while the western side remains steep and overgrown, preserving at least some of the character of the original approach.