Switzerland has enough underground nuclear bunkers to fit its entire population plus an extra 14 percent.

The Swiss government started this policy during the Cold War to protect citizens from nuclear war. As of 2022, the Swiss Federal Office for Civil Protection reported about 360,000 shelters. This includes 9,000 large public bunkers and over 350,000 private ones built into basements. These spaces can hold nearly 9 million people, which is more than the country's population of 8.6 million.The Sonnenberg Tunnel in Lucerne was once the largest civilian shelter in the world. It could hold 20,000 people and had its own hospital and radio station. Most bunkers use reinforced concrete walls at least 30 centimeters thick. They have heavy steel doors and air filters to block out dangerous chemicals or radiation.In 2011, the law changed so that very small houses do not have to build their own bunkers. Instead, those owners pay a fee to the local government to save a spot in a public shelter. On normal days, people use these rooms for storage, wine cellars, or band practice. However, the law says these rooms must be ready for an emergency within 48 hours.