Within the United Kingdom are the ruins of prehistoric structures and ancient neolithic settlements. The architecture of ancient Rome penetrated Roman Britain with "elegant villas, carefully planned towns and engineering marvels like Hadrian's Wall". After the Roman departure from Britain in around the year 400, Romano-British culture flourished but left few architectural remnants, partly because many buildings were made of wood, and partly because the society had passed into the Dark Ages. Similarly, Anglo-Saxons brought a "sophisticated building style of their own" to Britain, but little physical evidence survives because the principal building material was wood.