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
England–Wales border England–Wales border The England–Wales border, sometimes the Wales–England border or the Anglo-Welsh border, is the border between England and Wales, two constituent countries of the United Kingdom. It runs for , from the Dee estuary, in the north, to the Severn estuary in the south. It has followed broadly the same line since the 8th century, and in part that of Offa's Dyke; the modern boundary was fixed in 1536, when the former marcher lordships which occupied the border area were abolished and new county boundaries were created. The administrative boundary of Wales was confirmed in the Local Government Act