Seversk (Russian: Се́верск SYEH-veersk) is a city that lies to the north of Tomsk, Siberia. Seversk was once known as "Tomsk-7", a secret closed city of Russia. Tomsk-7 was off-limits to tourists and only became known after the fall of the iron curtain. Its main purpose was to drive the nuclear war machine of the Soviet Union, producing plutonium and highly enrriched uranium. It is home to the Siberian Chemical Combine.