Behind the walls of a forbidden city, the only thing more dangerous than its secrets is the truth.

City 40

Hidden in the heart of Russia, there is a Soviet-era city where thousands of people live and work behind barbed-wire fences monitored by armed guards. It is Ozyorsk (Ozersk), located in the Chelyabinsk Oblast, one of the most polluted places on the planet and home to the largest stockpiles of nuclear material. Its code name: City 40.