Just found this after looking at the Maus:
http://en.wikipedia.org/wiki/Karl-Ger%C3%A4t
Not a tank. A self-propelled 600mm mortar. Sends a chill down my spine.
And every time I see the word Gerat I immediately think Balkan-Gerat. 
@danasan - Thank you for sharing pics from your tanker days.
EDIT:
Eye candy. Building in Warsaw after hit from the Karl Device.
