The A478 road is a major road in Wales. The route is from its junction with the A487 at Cardigan, Ceredigion, to Tenby, Pembrokeshire. It crosses the Preseli Hills and winds through farmland for almost all of its route. The road just touches the very west of Carmarthenshire.

Cardigan is a town and community in the county of Ceredigion, Wales. Positioned on the tidal reach of the River Teifi at the point where Ceredigion meets Pembrokeshire, Cardigan was the county town of the historic county of Cardiganshire. Cardigan is the second-largest town in Ceredigion. The largest town, Aberystwyth, is one of the two administrative centres; the other is Aberaeron.