The largest tanks ever built were the 188 and 203 ton Maus tanks found at Kummersdorf in 1945. Hitler had ordered the original Porsche 205 design way back in 1942 for ultra-heavy tanks but work was slow finding the right engines and suspension to carry the excessive weight with enormous ground pressure. By 1943 work had begun at Alkett on two prototypes, but the air-cooled engines could not be fitted. A special 1080 hp MB509 aircraft engine was fitted to prototype 1 while prototype 2 took a marine MB517 diesel after blowing the first engine! Only prototype 1 was ever completed by 1944 with a 75 and 128mm co-axial system and armor protection all around averaging around 200mm (8 in)!!! The mantlet was 240mm (almost 10 in)! The Beast was slow at 8-10 mph and if it needed to cross a river then it could submerge with schnorkel to 8m with a power cable running from another Maus on the shore! Basically, these tanks were armored fortresses and besides the two prototypes the Red Army found 9 others partially completed upon surrender. One is on display in the Kubinka Armor Museum. In battle, no Soviet nor any Western tank would be able to penetrate it. In the West the Allies would have tried to bomb it or shoot 6" rockets at it... but the armor still might have stood up. For hunting, the Maus carried 232 rounds of ammo as opposed to 72 for the King Tiger (32 for the 128 mm + 200 for the 75mm and 1000 rds for the MG-34)! Believe it or not but Henschel had a rival in the 140 ton E-100 which was captured by the British with only the hull completed in 1945! That would have mounted a 170mm KwK44 with 200 rds and had armor of between 150-240mm! After that, there were plans for a PzKpfw IX which would bring the weight back down to standard heavy tank size. The reasonable PzKpfw VII Lowe (Lion) was passed over by Hitler for the Maus (PzKpfw VIII) b/c it wasn't impressive enough with armor at 100mm and initial 75mm gun...