Original: In 462 the Romans officially ceded Septimania to the Visigothic king Theodoric II who had held Carcassonne since 453; he built more fortifications at Carcassonne, which was a frontier post on the northern marches: traces of them still stand.
Simplified: In 462 the Romans officially left and the Visigothic king Theodoric II built more fortifications at Carcassonne, some of them still stand.