Closed city

A closed city or town is a settlement where travel or residency is restricted. In the Soviet Union, closed cities were quarantined for research and military purposes. Many of them have stayed closed in Russia and some post-Soviet states. The concept exists in other countries as well.

Historically, the construction of closed cities became increasingly common after the beginning of the Cold War, particularly in the Soviet Union. Since the dissolution of the Soviet Union in 1991, they remain widespread in Russia and some of the other post-Soviet states. The Russian government officially designates these closed cities as "closed administrative–territorial formations" (ZATO; Russian: закрытые административно–территориальные образования [ЗАТО]), for the management and execution of high-value research and development concerning nuclear energy, weapons of mass destruction, or the space industry.