After World War II, Switzerland began building homes with 40 cm-thick concrete ceilings that might survive firebombing of the type that destroyed Hamburg and Dresden. In the 1960s they began constructing radiation and blast shelters that could survive one to three bars (100–300 kPa) of pressure from a nuclear explosion. Building codes require blast shelters, which are said to be able to accommodate 114% of the Swiss population. Small towns have large underground parking garages that can serve as sealed community shelters. There are also hospitals and command centres in such shelters, aimed at keeping the country running in case of emergencies. Every family or rental agency has to pay a replacement tax to support these shelters, or alternatively own a personal shelter in their place of residence; many private shelters serve as wine cellars and closets.