The architecture of Scotland includes all human building within the modern borders of Scotland, from the Neolithic era to the present day. The earliest surviving houses go back around 9500 years, and the first villages 6000 years: Skara Brae on the Mainland of Orkney being the earliest preserved example in Europe. Crannogs, roundhouses, each built on an artificial island, date from the Bronze Age and stone buildings called Atlantic roundhouses and larger earthwork hill forts from the Iron Age.