This is a roughly rectangular fortified enclosure occupying a low knoll rising above low lying marshy ground. There is said to have been a paved road leading to the enclosure and dressed stone is said to have been found on the site (Lewis 1912). A section was dug across the north-west side in 1965 (Journal of Roman Studies 56 (1966), 196) revealing a 3.3m wide ditch and a turf revetted bank. The enclosure survives as an earthwork, but is more fully known from aerial (CUCAP) and geophysical (Hankinson & Jones 2007) survey. Excavations in 1965 by G.D.B. Jones and M.G. Jarrett revealed a ditch but no internal features and the excavators favoured the explanation that it was a very short-lived marching camp.

The enclosure is roughly 165m north-west to south-east by up to 130m. Parts of the south-west and north-west sides can be traced as earthworks. The former appears from the geophysical survey to be made up of an array of slight parallel linear features whilst the latter survives as a prominent double scarp representing a rampart backed by what is probably a linear quarry hollow. These two sides are joined by a distinctive canted angle whilst the southern corner appears to be rounded. On the northeast side the enclosure now rests on the steep scarp overhanging the Black Brook.

Although the Gaer is commonly identified as a Roman military site the form of the enclosure, revealed through aerial and geophysical survey, does not resemble that of any known Roman military work. No Roman material has been recovered from the site and early reports of a paved road and dressed stone may not be accurate. It has therefore been suggested that it represents a large and powerful later Prehistoric style settlement enclosure.

The supposed Roman road between Castell Collen and Caersws (NPRN 304960), passes close by on the south-west, but does not connect with the site, but RCAHMW aerial reconnaissance in March 2010 discovered two Roman practice camps some 335m south of The Gaer (NPRN 411812), perhaps indicating that this is, after all, a Roman site.


Sources: Lewis in Archaeologia Cambrensis 6th series 12 (1912), 168
Jarrett 'The Roman Frontier in Wales', 2nd edition (1969), 138-40
Hankinson & Jones 'Roman Military Sites in NE & E Wales' (2007), Clwyd-Powys Archaeological Trust report No. 854, 8

John Wiles, RCAHMW, 17 January 2008 and T. Driver, RCAHMW, 18 October 2010.

Royal Commission aerial reconnaissance in drought conditions on 9th July 2018 recorded a small circular feature some 450m N of the camp or fort. While this resembles the morphology of a round barrow, the parched response suggests buried stony footings for a circular monument. One interpretation, so close to a probable Roman camp or fort, is a small Roman tomb.

T. Driver, RCAHMW, 2023