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 Dee, Wales River Dee, Wales The River Dee (, ) is a river in the United Kingdom. It flows through parts of both Wales and England, forming part of the border between the two countries. The river rises in Snowdonia, Wales, flows east via Chester, England, and discharges to the sea in an estuary between Wales and the Wirral Peninsula in England. It has a total length of . The River Dee was the traditional boundary of the Kingdom of Gwynedd in Wales for centuries, possibly since its founding in the 5th century. It was recorded in the 13th century as "flumen