 Each of the 3 historic counties is therefore listed separately, and each of these has two lists - one for the prehistoric sites and one for the Roman, medieval and post-medieval sites.This list shows the sites dating to Roman, medieval and post-medieval times in Radnorshire, which occupies the central third of Powys.The River Wye separates it from Brecknockorshire to the south, and Montgomeryshire forms the northern third of Powys.