This rather small fort lies on a partly-augmented knoll at the mouth of Ewyn Brook valley, on the flat alluvial plain west of the Afon Rhiangoll. The fort platform is currently occupied by the buildings of Pen-y-gaer Farm in its eastern third and Greenhill Farm in its north-western corner angle; the somewhat winding lane which crosses the eastern half of the site may represent the general line of the via principalis and if this is the case, then the fort faced along the Ewyn valley to the ENE. The site was proven to be Roman during trial excavations conducted by D.W. Crossley in 1966 and subsequently published in Archaeologica Cambrensis (CXVII, 1968, pp.21/2).

The fort measures about 420 feet from ENE to WSW by 295 feet transversely (c.128 x 90 m), and therefore covers an area of only around 2¾ acres (c. 1.15 ha), which is rather small. Three building periods were noted in the construction of the defences:

  1. The original defensive enclosure consisted of a soil and stone rampart bank 25 feet (c.7.6 m) wide, revetted by stout timbers at the front and a stone kerb at the rear. No accompanying ditches were found but all traces may have been removed during later phases of construction.
  2. The primary rampart was topped at a later date by a stone wall about 3½ feet (c.1 m) wide but of unknown height, the rampart bank at the rear evidently raised to the same level at this time.
  3. The original stone wall and rampart was destroyed and a wider wall installed upon the terrace of demolition material. This new stone rampart was separated by a narrow berm from a V-shaped defensive ditch about 10 feet wide and 3½ feet deep (c.3 x 1 m). The fragmentary remains of stone and timber buildings within the interior of the fort probably all date to this period.

Finds from the interior of the fort include “well-worked” building stones, pieces of cement, pottery sherds and urns, the stone foundations of several buildings, also several Roman coins, including those of Nero (dated c. A.D. 67), Marcus Aurelius ( A.D. 145-61), Constantine I (c. A.D. 307/8) and Constantius II ( A.D. 332/3). The pottery finds suggest a foundation date sometime during the campaigns of governor Sextus Julius Frontinus (c. A.D. 73-8), with the stone rampart being added during the reign of Trajan (Imp.98-117). The presence of the later Roman coins points to some sort of continuing occupation of the site after the withdrawal of the original garrison, which possibly occurred sometime during the reign of Hadrian, as potsherds, bricks and tiles all dated c. A.D. 80-130 were found in the upper fill of the defensive ditch, and there were no proveable Antonine sherds recovered.

The Roman Garrison

The garrison was very likely a cohors quingenaria peditata, a regiment of a nominal 500 foot soldiers, which were evidently quartered in rather cramped conditions. It is possible, however, that the garrison unit – the identity of which remains unknown – was under-strength at the time the Pen-y-gaer fort was occupied.

RIB 401 - Centurial stone of Peregrinus

The century of Peregrinus built (this).


There is a Roman military settlement at Pen-y-Gaer, about 1.6 km. north-west of Tretower (see Nash-Williams Roman Wales rev. 2d ed., (1969) 108-110). A necessary connexion between this inscription, RIB 402, and this site is therefore not yet proven. If they came from farther afield, then Y Gaer, Brecon (19 km. to the north-west), or Abergavenny (13 km to the south-east) are the likely sources. Addenda from RIB+add. (1995): The same century may be named in RIB 1347 (Benwell) and 1376 (the Vallum near Benwell).

RIB 402 - Centurial stone of Valens

The century of Valens (built this).


For a note on the site from which it came see RIB 401.

References for Pen Y Gaer

  • Air Reconnaissance in Britain, 1973-76 by J.K. St. Joseph in J.R.S. lxvii (1977) pp.150/1;
  • Inventory of the Ancient Monuments in Wales – County of Brecknock by the RCAHMW (HMSO, London, 1986) pp.146-9 & figs.167-70.
  • The Roman Inscriptions of Britain by R.G. Collingwood and R.P. Wright (Oxford 1965);

Map References for Pen Y Gaer

NGRef: SO1621 OSMap: LR161

OS National Grid Reference: SO168219
Dimensions: c.420 x 295 ft (c.128 x 90 m)
Area: c.2¾ acres (c.1.15 ha)

Roman Roads near Pen Y Gaer

SE (9) to Gobannivm (Abergavenny, Gwent) NW (11) to Y Gaer (Brecon Gaer, Powys)

Sites near Pen-y-Gaer Roman Fort