Offa's Dyke is an old earthwork boundary between England and Wales built by order of King Offa of the ancient kingdom of Mercia. The Offa's Dyke Path, a National Trail, has been created following the line of the dyke. Many walkers will know of this trail and original parts of the dyke can still be seen in the Kington area. The trail leads over marvellous countryside with panoramic views. You can find lots of information on Offa's Dyke Path at National Trails.
The ODP can now be linked to the Wye Valley Walk by following Vaughan's Way from Kington to Bredwardine - as detailed in "Walking with a Greyhound in Herefordshire in Wales" published in 2002. This route is fully waymarked.