The Romano-British populations of Wales, the Westcountry, and Cumbria experienced a degree of autonomy from Anglo-Saxon influence, represented by distinct linguistic, liturgical and architectural traditions, having much in common with the Irish and Breton cultures across the Celtic Sea, and allying themselves with the Viking invaders. This was however, gradually elided by centuries of English dominance. Characteristically circular buildings as opposed to rectangular, often in stone as well as timber, along with sculptured Celtic crosses, holy wells and the reoccupation of Iron Age and Roman sites from hillforts such as Cadbury Castle, promontory hillforts such as Tintagel, and enclosed settlements called Rounds characterise the western Sub-Roman Period up to the 8th century in southwest England and continue much later in independent Wales at post-Roman cities such as Caerleon and Carmarthen.