Tzar Tank

Read it and weep! Landships describes the Biggest Tank Ever Built! It is also the Most Strange Armored Fighting vehicle ever constructed. "Lebedenko Tank", or Tzar tank (after tsar Nikolaj, who helped finance it) was also called "Netopyr" - vampire bat.
Its history starts in 1914 with the engineer N. Lebedenko, who came up with the idea of a 40-ton battle machine, running on one small and two very large spoked wheels, almost 9 meter in
diameter. The designers hoped that this configuration would make it
possible for the vehicle to cross practically all obstacles. However on
the initial trial run the small wheel got stuck in a ditch, and the weak
engines did not help either.

http://www.darkroastedblend.com/2007/03/strange-tanks.html