The German Panzerkampfwagen VIII "Maus" (Mouse).
There were 5 of these massive tanks ordered but only 1 was ever fully completed. That one never made it into combat.
The Maus weighed 207 tons/188tonnes. Length = 33 feet 6 inches, width = 12 feet 2 inches, height 11 feet 11 inches.
The main gun was a "KWK 44" 5 inch/128mm. Top speed was 12mph/20km/h.