Russia's secret nuclear facility at Mt. Yamantau

The Yamantau Mountain complex is located close to one of Russia's remaining nuclear weapons labs, Chelyabinsk-70. Two entire cities have been constructed over the site, known as Beloretsk 15 & 16 which are closed to the public, each with 30,000 workers. No foreigner has ever set foot near the site. Thumbnail is of the entrance to the mountain complex.