“Crannogs are a type of ancient loch-dwelling found throughout Scotland and Ireland, while one has been discovered in Wales in Llangorse Lake. Most are circular structures that seem to have been built as individual homes to accommodate extended families. Other types of loch settlements are also found in Scandinavian countries and throughout Europe” – SCC
They date from 5,000 years ago and were in use until the 17th century.
This one (restored obviously) is near Kenmore, on Loch Tay