Many of you have probably seen this revolver before, but I had not. The gigantic wheel gun measures four feet in length!
It was build by Ryszard Tobys and was modeled after the Remington Model 1859 revolver. It is 28mm in caliber (1.1″)!
Thanks to Sven for the link.
Hat Tip: Weapons Blog
UPDATE: Added corrected information and photos. Thanks pauloos for the link.