Closed city

A closed city or town is a settlement where travel or residency restrictions are applied so that specific authorization is required to visit or remain overnight. Such places may be sensitive military establishments or secret research installations that require much more space or internal freedom than is available in a conventional military base.^{[citation needed]} There may also be a wider variety of permanent residents, including close family members of workers or trusted traders who are not directly connected with clandestine purposes.

Many closed cities existed in the Soviet Union during the Cold War.^[1] Following the dissolution of the Soviet Union in 1991, a number of them continue to exist in the post-Soviet states, especially in Russia. In modern Russia, such places are officially known as "closed administrative-territorial formations" (Russian: закрытые административно-территориальные образования [ЗАТО], romanized: zakrytye administrativno-territorial'nye obrazovaniya [ZATO]).^[2]