Topic: Russia/human geography of Russia
A closed city or closed town is a settlement where travel or residency restrictions are applied so that specific authorization is required to visit or remain overnight. They may be sensitive military establishments or secret research installations that require much more space or freedom than is available in a conventional military base. 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 its clandestine purposes.
Many closed cities existed in the Soviet Union until its collapse in 1991. After 1991, a number of them still existed in the CIS countries, especially Russia. In modern Russia, such places are officially known as "closed administrative-territorial formations" (закрытые административно-территориальные образования, zakrytye administrativno-territorial'nye obrazovaniya, or ЗАТО ZATO for short).