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A closed city or closed town is a settlement with travel and residency restrictions in the Soviet Union and some of its successor countries. 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).
Closed cities were not represented on any maps, except classified ones. There were no road signs or similar designations for closed cities, and they were omitted from railroad time tables. Bus routes to closed cities were shown as going to a nearby tiny village, with the stop nearest the closed city named "47km" etc. For mail delivery, a closed city is usually named as the nearest large city and a number, e.g. Arzamas-16, Chelyabinsk-65. These can be rather distant from their namesakes, for instance, Sarov, designated Arzamas-16, is in the federal republic of Mordovia, whereas Arzamas is in the Nizny Novgorod region (roughly 75 km away). People not dwelling in a closed city were subject to document checks and security checkpoints, and explicit permission was required for them to visit. To relocate to the closed city, one would need security clearance by the KGB.
The closed city was sometimes guarded by a security perimeter with barbed wire and towers, much like a prison. This did not limit the freedom of the residents, who could easily cross the perimeter via the security checkpoint. The very fact of such a city's existence was often classified, and residents were expected not to divulge to outsiders their place of residence. This lack of freedom was often compensated by better housing conditions and a better choice of goods in retail trade than elsewhere in the country. Also, in the USSR, people working with classified information received a salary bonus.
The "box" 
The "box" was the unofficial name of a secret Soviet facility much like the closed city, but smaller, usually the size of a factory. The "box" name was usually classified, as were the activities there. Incoming mail was addressed to "mailbox #XXXX", thus the name of "box". Most Soviet design bureaus for weapons, aircraft, space, military electronics and such were "boxes".
Closed cities were established from the late 1940s onwards under the euphemistic name of "post boxes", referring to the practice of addressing post to them via mail boxes in other cities. They fell into two distinct categories. The first category comprised relatively small communities with sensitive military, industrial or scientific facilities, such as arms plants or nuclear research sites. Examples are the modern towns of Ozyorsk (Chelyabinsk-65) with a plutonium-production plant, and Sillamäe, the site of a uranium enrichment facility. Even Soviet citizens were not allowed access to these places without proper authorization. In addition to this, some bigger cities were closed for unauthorized access to foreigners, while they were freely accessible to Soviet citizens. These include cities like Perm, a center for Soviet tank production, and Vladivostok, the base of the Soviet Pacific Fleet.
The second category consisted of border cities (and some whole border areas, such as the Kaliningrad Oblast and Saaremaa and Hiiumaa) which were closed for security purposes. Comparable closed areas existed elsewhere in the Soviet bloc; a substantial area along the inner German border and the border between West Germany and Czechoslovakia was placed under similar restrictions. Citizens were required to have special permits to enter such areas.
The locations of the first category of the closed cities were chosen for their geographical characteristics. They were often established in remote places situated deep in the Urals and Siberia, out of reach of enemy bombers. They were built close to rivers and lakes which were used to provide the large amounts of water needed for heavy industry and nuclear technology. Existing civilian settlements in the vicinity were often used as sources of construction labor. Although the closure of cities originated as a strictly temporary measure which was to be normalized under more favorable conditions, in practice the closed cities took on a life of their own and became a notable institutional feature of the Soviet system.
Movement to and from closed areas was tightly controlled. Foreigners were prohibited from entering them and local citizens were under stringent restrictions. They had to have special permission to travel there or leave, and anyone seeking residency was required to undergo vetting by the NKVD and its successor agencies. Access to some closed cities was physically enforced by surrounding them with barbed wire fences monitored by armed guards.
Ukraine had eleven closed cities: among them the Crimean port of Sevastopol and the industrial city of Dnipropetrovsk, though both were restricted to foreigners, not locals. Travel restrictions were lifted in the mid-1990s.
There were two closed cities in Estonia: Sillamäe and Paldiski. As all the other industrial cities, the population of them was mainly Russian-speaking. Sillamäe was the site for a chemical factory that produced fuel rods and nuclear materials for the Soviet nuclear power plants and weapon facilities, while Paldiski was home to a Soviet Navy nuclear submarine training centre. Sillamäe was closed until Estonia regained its independence in 1991; Paldiski remained closed until 1994, when the last Russian warship left.
Closed cities today 
The policy of closing cities underwent major changes in the late 1980s and early 1990s. Some cities, such as Perm, were opened well before the fall of the Soviet Union; others, such as Kaliningrad and Vladivostok, remained closed until as late as 1992. The adoption of a new constitution for the Russian Federation in 1993 prompted significant reforms to the status of closed cities, which were renamed "closed administrative-territorial formations" (or ZATO, after the Russian acronym). Municipally, all such entities have a status of urban okrugs, as mandated by the federal law.
There are currently 42 publicly acknowledged closed cities in Russia with a total population of about 1.5 million people. 75% are administered by the Russian Ministry of Defense, with the rest being administered by the Russian Federal Atomic Energy Agency, formerly the Ministry for Atomic Energy (Minatom). Another 15 or so closed cities are believed to exist, but their names and locations have not been publicly disclosed by the Russian government.
The number of closed cities in Russia is defined by government decree (see links below). They include the following cities:
- Amur Oblast: Uglegorsk
- Arkhangelsk Oblast: Mirny
- Astrakhan Oblast: Znamensk
- Republic of Bashkortostan: Mezhgorye
- Chelyabinsk Oblast: Ozyorsk, Snezhinsk, and Tryokhgorny
- Kamchatka Krai: Vilyuchinsk
- Krasnoyarsk Krai: Zelenogorsk, Norilsk, Zheleznogorsk and Dikson.
- Leningrad Oblast: Sosnovy Bor
- Moscow Oblast: Krasnoznamensk, Zvyozdny gorodok, Vlasikha
- Murmansk Oblast: Alexandrovsk, Ostrovnoy, Severomorsk, and Zaozyorsk
- Nizhny Novgorod Oblast: Sarov
- Penza Oblast: Zarechny
- Primorsky Krai: Bolshoy Kamen and Fokino
- Saratov Oblast: Shikhany
- Sverdlovsk Oblast: Lesnoy, Novouralsk, and Svobodny
- Tomsk Oblast: Seversk
- Vladimir Oblast: Raduzhny
Some of them are open for foreign investment, but foreigners may only enter with a permit. An example is the Nuclear Cities Initiative (NCI), a joint effort of the United States National Nuclear Security Administration and Minatom, which involves in part the cities of Sarov, Snezhinsk, and Zheleznogorsk.
The number of closed cities has been significantly reduced since the mid-1990s. However, on October 30, 2001, foreign travel (except for Belarusian citizens) was restricted in the northern cities of Norilsk, Talnakh, Kayerkan, Dudinka and Igarka. Russian and Belarusian citizens visiting these cities are not required to have travel permits.
Krasnoyarsk-26 in Siberia, researched for subject of Sidney Sheldon's 2001 fictional murder mustery-romance The Sky is Falling, was planned in 2003 to be shut down by 2011,  in co-operation with the U.S, and documented by their National Resources Defense Council, but actually closed in 2008.
Three closed cities under Russian administration exist in Kazakhstan. They are Baikonur (formerly Leninsk), a city constructed to service the Baikonur Cosmodrome, the Kurchatov township at the Semipalatinsk Test Site and Priozersk which is the administrative center of the Sary Shagan anti-ballistic missile testing site.
- Oak Ridge, Tennessee was a US closed city during the Manhattan Project.
- Mercury, Nevada is currently closed as part of a test site.
See also 
- Gated community
- Internal passport
- Mercury, Nevada, U.S.A.
- Nuclear Cities Initiative
- Quantico, Virginia (home page)
- Los Alamos, New Mexico
- "City border". Photoarchives. FOTOESCAPE. Retrieved 2013-03-16.
- "Secret Cities." Globalsecurity.org. Accessed August 2011.
- Victor Zaslavsky, "Ethnic group divided: social stratification and nationality policy in the Soviet Union", p.224 in Peter Joseph Potichnyj, The Soviet Union: Party and Society, Cambridge University Press, 1988. ISBN 0-521-34460-3
- Nadezhda Kutepova & Olga Tsepilova, "A short history of the ZATO", p. 148-149 in Cultures of Contamination, Volume 14: Legacies of Pollution in Russia and the US (Research in Social Problems and Public Policy), eds. Michael Edelstein, Maria Tysiachniouk, Lyudmila V. Smirnova. JAI Press, 2007. ISBN 0-7623-1371-4
- Greg Kaser, "Motivation and Redirection: Rationale and Achievements in the Russian Closed Nuclear Cities", p. 3 in Countering Nuclear and Radiological Terrorism, eds. David J. Diamond, Samuel Apikyan, Greg Kaser. Springer, 2006. ISBN 1-4020-4897-1
- isbn 0446610178 "The Sky is Falling" by Sidney Sheldon 2001
- (Russian) Current list of (acknowledged) closed cities/areas from the Russian Federation Administration website[dead link]
- Russia’s closed cities are open and shut case - article from Russia Journal. (original source requires paid subscription )
- National Nuclear Security Administration, U.S. Dept. of Energy website
- "Secret Cities" (article), from Globalsecurity.org
- Secret / Closed Cities in Google Earth
- Right to the city in former Soviet Union closed cities (ZATO) Andrius Ropolas' paper focusing upon the social aspects of closed cites. Helpful bibliography.