The Panzer VIII Maus was a German super-heavy tank design, and the heaviest tank to reach the complete working prototype stage in World War II.
The tank's hull was 33 ft 2 in long, 12 ft wide and 12.0 ft tall. Weighing about 180 tonnes, the Maus's main armament was a 128mm (5.0 in) cannon with a coaxial 75mm (3.0 in) gun and steel armor ranging from 60–240 mm (2.4–9.4 in) in thickness. A total of nine were in various stages of completion and two were completed when the war ended, although one version had a planned production run of between 150 and 200. The Maus would have had a crew of five to six.
The amount of armour was substantial, the front lower hull was about 200 mm (7.9 in) thick, sloped at 35 degree angle. The sides of the hull were 180 mm (7.1 in) and the rear 160 mm (6.3 in). The turret was 240 mm (9.4 in) to the front and 200 mm (7.9 in) to the sides, with a roof of 60 mm (2.4 in).
The Maus tank was originally designed to weigh approximately 100 tons and be armed with a 128 mm main gun and a 75 mm co-axial secondary gun. Additional armament options were studied including various versions of 150 mm and 128 mm guns. Hitler himself in January 1943 insisted that the armament be a 128 mm main gun with a coaxial 75 mm gun.
By May 1943, a wooden mockup of the final Maus configuration was ready and presented to Hitler, who approved it for mass production, ordering a first series of 150. At this point, the estimated weight of the Maus was 188 tons. However, there is a story that concerns the main armament of the Maus being changed by Hitler who said that the 128 mm gun looked like a ´toy gun´ when compared to the tank, causing the 128 mm to be replaced by a 150 mm gun.
The principal problem with the Maus that emerged from this test was its power-to-weight ratio. There was no engine powerful enough to give it anything like the 20 km/h demanded by the design specifications. The modified gasoline-fuelled Daimler-Benz MB 509 engine used in the prototype was only able to move at 13 km/h and only under ideal conditions. The suspension system used by the Maus also had to be adjusted to enable it to take the tank's weight.
Another issue found was that the Maus was simply too heavy to cross bridges. As a result an alternative system was developed, where the Maus would instead ford the rivers it needed to cross. Due to its size it could ford relatively deep streams, but for deeper ones it was to submerge and drive across the river bottom. The solution required tanks to be paired up. One Maus would supply electrical power to the crossing vehicle via a cable until it reached the other side. The crew would receive air through a large snorkel, which was long enough for the tank to go 45 feet (13 m) underwater.
Once again all of this came from Wikipedia.