There are some closed cities in Russia, which can’t be visited by foreign citizens even if they really want.
Some of closed cities are closed not only for the foreigners but for Russians as well. You need a state pass to visit a closed city. Such passes usually are issued by authorities of a certain closed city.
In Russia as well as in other countries there are territories where are situated factories producing mass destruction weapon, processing radioactive materials or where are situated important military facilities. There are 38 closed towns in Russia as of 2020 (every year their quantity decreases).
Closed cities are regulated by the following governmental decrees:
- Mezhgorye (Republic of Bashkortostan)
- Sibirsky (Altai Krai)
- Zheleznogorsk (Krasnoyarsk Krai)
- Zelenogorsk (Krasnoyarsk Krai)
- Solnechny (Krasnoyarsk Krai)
- Fokino (Primorsky Krai)
- Tsiolkovsky (Amur Oblast)
- Mirny (Arkhangelsk Oblast)
- Znamensk (Astrakhan Oblast)
- Raduzhny (Vladimir Oblas)
- Vilyuchinsk (Kamchatka Krai)
- Pervomaisky (Kirov Oblast)
- Krasnoznamensk (Moscow Oblast)
- Voskhod (Moscow Oblast)
- Molodyozhny (Moscow Oblast)
- Vlasikha (Moscow Oblast)
- Zvyozdny gorodok (Moscow Oblast)
- Zaozyorsk (Murmansk Oblast)
- Ostrovnoy (Murmansk Oblast)
- Severomorsk (Murmansk Oblast)
- Vidyayevo (Murmansk Oblast)
- Alexandrovsk (Murmansk Oblast)
- Sarov (Nizhniy Novgorod Oblast)
- Komarovsky (Orenburg Oblast)
- Zarechny (Penza Oblast)
- Zvyozdny (Perm Krai)
- Svetly (Saratov Oblast)
- Lesnoy (Sverdlov Oblast)
- Novouralsk (Sverdlov Oblast)
- Svobodny (Sverdlov Oblast)
- Uralsky (Sverdlov Oblast)
- Ozyorny (Tver Oblast)
- Solnechny (Tver Oblast)
- Seversk (Tomsk Oblast)
- Ozyorsk (Chelyabinsk Oblast)
- Snezhinsk (Chelyabinsk Oblast)
- Tryokhgorny (Chelyabinsk Oblast)
- Gorny (Zabaykalsky Krai)
There are territories in the CIS countries which you can’t visit. The most famous is Baykonur (facility with cosmodrome and a town) in the Kazakhstan, Karshi-Khanabad military air base in the Uzbekistan and Ämari Air Base in the Estonia.
Closed administrative-territorial localities are surrounded around the perimeter by barbed wire and have checkpoints with security. So, if you enter Russia under tourist or private visa, don’t be afraid that you will accidentally go into a closed town.
If you have questions ask them in comments. I will try to answer them all.