In 1942, with German Army at the doors of Moscow, Samara (than Kuybishev) was named USSR second capital and it would have become the capital city, had Moscow fallen down to the German Army. Moscow eventually resisted, so Samara never became the capital city. But the great underground construction, known as Stalin's Bunker was built here. Soviet government with Stalin at the head was planed be moved into this bunker in case of Moscow defeat.
It was an important and top secret military object until 1990. The bunker is totally underground. Until 1990 the residents of the neighborhood don't even suspect there is such a mighty construction under their homes. The bunker was built in nine months of 1942. It's still a question how they managed to build such a great bunker inside the town without having anyone know anything about it. The general opinion is that secret underground constructions (there are many of them in Samara) were made by prisoners who were then shot.
In 1990 the bunker was turned into a museum, which was kind of sensation.
The bunker is about 40 meters deep (just to compare - the Hitler's bunker was only about 15 meters deep). Six hundred people were planed to be placed inside of the bunker. 
The bunker is an important historical heritage and you will have the feeling to smell the very essence of former Soviet Power here.
Stalin still has some cigars hidden down there.