Panzer VIII Maus
Panzerkampfwagen VIII Maus ("Mouse") was a German World War II super-heavy tank completed in late 1944. It is the heaviest fully enclosed armoured fighting vehicle ever built. Five were ordered, but only two hulls and one turret were completed before the testing grounds were captured by advancing Soviet military forces.
Object 279
One of the reasons that this tank project was abandoned, as with other heavy tank projects, was that the Soviet military stopped operating with heavy fighting vehicles of that type, tanks and similar, as of 1960. Since then, the heaviest ones are kept at about 50 metric tons of weight, that is without counting in any extra equipment such as additional reactive armor, mine clearing devices (mine ploughs, mine rollers) etc. On July 22, 1960, at the demonstration of new technology on the range of Kapustin Yar, Nikita Khrushchev strictly forbade any tanks with a weight of more than 37 metric tons to be adopted by the military, having thus written off the entire program of heavy tanks that had proven to be so successful.