This map shows the route of the Roman road, the Via Julia Montana. The route of the road is displayed in green.

The road is of pivotal importance to understanding the Roman occupation of Wales. It was part of quite an extensive Roman road network and ran from Carmarthen, through Brecon and Abergavenny, to Usk. Another route known as the Via Julia Maritima ran nearer the coast between Carleon, Neath and Carmarthen.

Other evidence of Roman roads has been identified, for example near Cynghordy, but further investigation is needed. These latter examples and others also lie within the pylon line construction corridor.

The red outline on the map shows Green Gen Cymru's proposals for a corridor of new electricity pylons.

In 1849, Samuel Lewis noted that "the route of the road rests only on conjecture, is thought by some to have entered [the county] from Brecknockshire...and thence proceeded by Llangadog and Llandeilo-Fawr, to Carmarthen, where it joined the Via Julia Maritima". By the end of the century, OS maps plotted the route through Carmarthenshire with greater confidence. Residents in the local area continue to refer to parts of this route as "the Roman road".