Inherited from the Soviet Union, these cities host important sites of the atomic, metallurgical, chemical and military industries.
They are called “forbidden cities” and “closed cities”, a Soviet phenomenon that still exists today. In modern Russia, most of these cities are now open, or almost …
The concept of “closed city” appeared in the USSR in the late 1940s and had a strict purpose: to serve the interests of large industrial groups, the army, or major research institutions. These are areas of production or extraction of minerals and natural gas in large quantities. It was not worth seeking these “economic boosters” on Soviet maps because they were not included. Simply designated by postal code, the closed cities were kept secret for long periods of time. Today most of them are known.
Russia has 42 of them. Together with the collapse of the Soviet State, they ceased to be secret, but it is likely there are more, unknown yet. They are called “ZATO” (closed administrative territorial entities). Surrounded by barbed wire, protected by armed guards, the entry of these secret areas is strictly forbidden to foreigners. Such prohibited cities are located in remote areas, without any official way to access them. To enter there, the Russians must have special permission. Moving out of these closed cities is also not easy, as you need a special document from the authorities.
One of them is the city of Ozersk. The “Mayak” processing center for storing nuclear waste is located near Ozersk, at about 1000 miles near Moscow. During the Soviet Era, Mayak was one of the main producers of plutonium for the nuclear arsenal. In 1957 a container with 80 tons of radioactive waste exploded there.

Sign at Ozersk reads “Contaminated zone. Entrance is prohibited” Image via svoboda.org
Thousands of residents were evacuated from the area, and many have perished since. Even now, large areas in the Ural region are uninhabited.
The Mayak center no longer produces plutonium, but today everything that happens in and around the city of Ozersk is strictly classified as a military secret. Civil and military production are still closely linked.
Zheleznogorsk, Krasnoyarsk Krai
The city of Seversk.
Sarov.
Images via skyscrapercity.com