This is a 400m stretch of Roman road running north-east from Plas-y-fan, part of the route between Coelbren and Brecon Gaer (RR622: NPRN 407127). It is visible as a slight AGGER or causeway, 0.25-0.3m high. RCAHMW aerial coverage shows a parched band flanked by the darker lines of roadside ditches and with several quarry pits also visible.
This is part of a 4.0km alignment, its line perpetuated to the south-west by a modern lane. The road is next recorded here some 1.6km to the north-east where it crosses the Nant-y-llest (NPRN 275631).

Sources: Jones in Archaeologia Cambrensis 106 (1957), 59-60
RCAHMW Brecknock Inventory: Prehistoric & Roman (1986), 161

John Wiles 06.12.07