SdKfz 2, better known as Kleines Kettenkraftrad HK 101 or Kettenkrad for short (Ketten means "chain" or "tracks" and krad is the military abbreviation of the German word Kraftrad, the administrative German term for motorcycle)
The 600 mm monster siege mortar Karl Gerat 040 "Odin" was self propelled and required its own escort tank chassis projectile carrier, seen here stopped next to it. Each shell was 24 inches in diameter and weighed 4,800 pounds; the mortar could hurl it at targets 6.2 miles away. During the war, the Germans built seven such guns and used them mainly in Russia. Only two of the seven survive today.