The Chepstow Castle ruins in Monmouthshire, Wales, on top of cliffs overlooking the River Wye, is the oldest surviving post-Roman stone fortification in Britain. Its construction was begun under the instruction of the Norman Lord William Fttzosbern, soon made Earl of Hereford, from 1067, and it was the southernmost of a chain of castles built along the English-Welsh border in the Welsh Marches.
monnow is the only remaining fortified river bridge in great britain with its gate tower standing on the bridge. the original bridge was constructed in the mid-12th century, with its timber dating to trees felled between 1123 and 1169. the stone finish and gate house were constructed in the late 13th century. in 1804, the monmouth antiquarian charles heath wrote that the bridge’s “foundation is so ancient that neither history or tradition afford any light respecting the date of its erection”.