walls and coastal forts such as those at Portchester, Pevensey and Burgh Castle, which have survived through incorporation into later castles. Other structures still standing include a lighthouse at Dover Castle, now part of a church. In most cases, only foundations, floors and the bases of walls attest to the structure of former buildings. Some of these were on a grand scale, such as the palace at Fishbourne and the thermae at Bath. The more substantial buildings of the Roman period adhered closely to the style of Roman structures elsewhere, although traditional Iron Age building methods remained in general use for humbler dwellings, especially in rural areas. Medieval architecture Anglo-Saxon architecture Architecture of the Anglo-Saxon period exists only in the form of churches, the only structures commonly built in stone apart from fortifications. The earliest examples date from the 7th century, notably at Bradwell-on-Sea and Escomb, but the majority from the 10th and 11th centuries. Due to the systematic destruction and replacement of English cathedrals and monasteries by the Normans, no major Anglo-Saxon churches survive; the largest extant example is at Brixworth. The main material is ashlar masonry, sometimes accompanied by details in reused Roman brick. Anglo-Saxon churches are typically high and narrow and consist of a nave and a narrower chancel; these are often accompanied by a west tower. Some feature porticus (projecting chambers) to the west or to the north and south, creating a cruciform plan. Characteristic features include quoins in "long-and-short work" (alternating vertical and horizontal blocks) and small windows with rounded or triangular tops, deeply splayed or in groups of two or three divided by squat columns. The most common form of external decoration is lesene strips (thin vertical or horizontal strips of projecting stone), typically combined with blind arcading. Notable examples of this exist at Earls Barton, Bradford-on-Avon and Barton-upon-Humber. Norman architecture In the 11th century the Normans were among Europe's leading exponents of Romanesque architecture, a style which had begun to influence English church building before 1066, but became the predominant mode in England with the huge wave of construction that followed the Norman Conquest. The Normans destroyed a large proportion of England's churches and built Romanesque replacements, a process which encompassed all of England's cathedrals. Most of the latter were later partially or wholly rebuilt in Gothic style, and although many still preserve substantial Romanesque portions, only Durham Cathedral remains a predominantly Romanesque