The document discusses traditional Hakka earthen buildings called "Tulou" located in Yongding County, Fujian Province, China. Tulou are large, round or square fortified earth buildings constructed between the 12th-20th centuries by the Hakka people for defense and living purposes. They used rammed earth techniques to build thick walls. The largest Tulou, ChengQi Lou, is 4 stories tall with 400 rooms. In 2008, 46 Tulou sites were named a UNESCO World Heritage Site.