I came across this great photo essay a while back regarding a unique and impressive form of housing found in rural China, the Tulou, used by the Hakka people.
The Tulou is typically a large enclosed building, rectangular or circular in configuration, with a very thick weight supporting earth wall (up to 6 feet thick) and wooden skeletons, between three and five stories high, housing up to 80 families. These earth buildings usually have only one main gate, guarded by 4 to 5 inch thick wooden doors reinforced with an outer shell of iron plate. The top level of these earth buildings has gun holes for defense against bandits. They are a testament to the unique cultures that exist throughout China.