Hay-on-Wye the north-easternmost tip of the Brecon Beacons National Park, just north of the Black Mountains. The town is just on the Welsh side of the border with Herefordshire, England, here defined by the Dulas Brook. Where the brook joins the River Wye just north of the town, the border continues northwards along the river. The Wye was the boundary between the former counties and districts of Radnorshire and Brecknockshire. The adjacent village of Cusop lies on the English side of the Dulas Brook. The nearest city is Hereford, county town of Herefordshire, some to the east. The Royal Mail depot
River Monnow River Monnow The River Monnow () marks the England–Wales border for much of its length. After flowing through southwest Herefordshire, England, and eastern Monmouthshire, Wales, its confluence with the River Wye is approximately south of Monmouth. The Monnow rises near Craswall on Cefn Hill just below the high Black Mountains, Wales. It flows southwards, gaining the waters of its tributaries the Escley Brook and Olchon Brook near Clodock and the waters of the River Honddu, from the Welsh side of the Black Mountains, near Pandy. The river then flows briefly eastwards, to Pontrilas, where it is joined by its largest