Anglo-Saxon architecture was a period in the history of architecture in England from the mid-5th century until the Norman Conquest of 1066. Anglo-Saxon secular buildings in Britain were generally simple, constructed mainly using timber with thatch for roofing. No universally accepted example survives above ground. Generally preferring not to settle within the old Roman cities, the Anglo-Saxons built small towns near their centres of agriculture, at fords in rivers or sited to serve as ports. In each town, a main hall was in the centre, provided with a central hearth.