The idea of the diaolou, some 1,800 of which are still standing, has been around for centuries, but most were built during the 1920s and 1930s. At that time, China was full of bandits and warlords, so many overseas Chinese sent money home to build fortresses for their families. The diaolou are built to withstand assault; with barred gates, iron shutters, and many stories of stone, they are imposing structures.