There are three co-joined earthwork enclosures at Coed-y-Caerau, Pen Toppen Ash. They are set along the summit crest of a steep ridge above the left bank of the lower Usk. The south-western enclosure is roughly oval, about 84-94m in diameter, defined by a single bank, with an apparent inturned entrance, having traces of an outer circuit on the south and south-west. The central enclosure is sub-circular, about 74-80m in diameter, defined by what appears to be a partially spiralling bank, within a roughly concentric outer embanked enclosure, that springs from the south-west enclosure circuit, about 136-142m in diameter, counterscarped on the north-west and having inturned entrances on the south-east and north-east.

The north-eastern enclosure is possibly a Roman fortlet, though an Iron Age date seems more likely given its association with the other Iron Age features. It is rectangular, about 96m north-east to south-west by 108m, and defined by a single bank with rounded angles. An outer, roughly concentric circuit, generally 166m square, appears to respect the central enclosure.

Sources: Os495card; ST39SE39;
Jarrett 1969 'the Roman Frontier in Wales' 2nd ed., 81.

J.Wiles, RCAHMW, 14 February 2003