One of the most famous groups of 'tulou', or fortified Hakka clan houses, called the Tianluokeng group, in Fujian Province, China. Tulou are fortified, adobe (earth) Hakka clan houses, many of them circular like this one, found only in the hills of Fujian Province in southern China. This unique architecture evolved as a means of defence when the Hakka migrated to this region beginning in the 13th century. A few thousand tulou remain today in use. These are in Shangbang Village, Shuyang Town, Nanjing County.