USSR Battle Mole – This is probably an urban legend, because all sources are very unreliable and controversial.. According to some authors, Soviet Union like Nazi Germany and the USA had projects of Subterrenes in 1930s and 1960s. At least we have article about them in Russian Wiki.
“Photo” of this device near Ural mountain “Blagodat’ ” in 1930s.
In the time of the arms race, the Soviets sought ways to deliver nuclear weapons in the U.S. One possible way was to deliver nuclear bomb under ground. It is believed that such devices could even have a nuclear power engine.
In 1964, the plant was built and produced the first Soviet atomic underground boat, called “Battle Mole.” Underground boat had titanium case with a pointed bow and stern diameter of 3.8 m and a length of 35 m crew consisted of 5 people. In addition, she was able to take on 15 other people landing and a ton of explosives. Main power plant – nuclear reactor – let her develop speed underground to 7 km / h Its combat mission was to destroy underground command centers and enemy missile silos.
The first tests of the “fighting mole” in the autumn was in 1964. Underground boat showed amazing results, passing a difficult ground “like a knife through butter” and destroying underground bunker of imaginary enemy.
Fantasy of modern painter:
Further testing continued in the Urals, in the Rostov region, and in more solid ground near the Moscow. Likely, this is the hole after device testing:
Authors of stories claim that during the tests an incident occurred and the project was canceled..