German prototype PzKpfw 10 super tank with curved armour. Panzer IX and Panzer X only existed as projects on drawing boards. Although, there is no real blueprints showing the realistic look of both vehicles. PzKpfw X was to be wider but lower than Maus and was to be surely armed with 88mm or even 128mm gun. Both designs were very advanced and modern including many features which can be found in modern tanks of today.