|SW (4) to Castell Collen (Powys)
N (19) to Caersws (Caersws, Powys)
|SO018665||c.450 x 400 ft
(c.137 x 122 m)
The remains of the south-west and north-west defences of this fort are still visible in fields in Nantmel parish just to the south of the A44 road between Rhayader and Crossgates. A section through the defences in 1965 revealed the remains of a turf-revetted rampart, only 4 feet (c.1.2 m) wide, fronted by a V-shaped ditch 11 feet (c.3.3 m) across. These defences measured about 450 feet by about 400 feet (c.137 x 122 m) and enclosed an area of just under 4¼ acres (c.1.67 ha). No dating evidence and no evidence of internal structures were found during excavations.
The fort is sited on a small knoll (@ 224m OD) with the Black Brook delimiting it's north-eastern defences. The slight nature of its defences and the lack of any permanent buildings in its interior suggest that the fort was only occupied for a short period before being abandoned. The temporary marching camp about a mile to the north of the fort at Trefal, lies (c.255m OD) on a wide, flat ridge on the eastern flank of Castle Hill (388m OD) and is superbly placed for an assault on this prominence, but no trace of any 'castle' was observed in 1911 when the summit and flanks of the hill were surveyed prior to the publication of the Inventory of the Ancient Monuments in Wales and Monmouth III - County of Radnor in 1913.