Built in the late 8th century by Offa, king of Mercia, Offa’s Dyke marked the boundary between England and Wales. It is the longest archaeological monument in Britain. Comprising a large earth rampart on the English side and a deep ditch on the Welsh side, the dike runs some 240 km (150 mi) from the mouth of the River Wye in the south to Basingwerk on the River Dee in the north. This photograph was taken near the village of Newcastle in Shropshire.
