I just found this video. It is a giant one wheeled vehicle.
what an odd vehicle
kinda pointless cause you can’t turn lol.
But it is quite weird.
I seen that thing before on the interwebs, but I can’t remember how where or why.
From memory the guy who built it was working towards breaking the one wheeled vehicle land speed record. Hence turning wasn’t much of a concern but speed was. I’ve seen footage of it going much faster 
For full info see:
I remember reading on his site he was considering building another model to beat the speed record. However he’s going to have a tough time beating the Maclean Rocket Roadster
arcin and sparkin
Makes me want to go out to the shop and BUILD!.. somthing. I don’t know what but… maybe a steam powered unicycle!!! You may laugh but I wouldn’t be supprised if that guys great grandfather got looking at someones bicycle and said “well…why not it’ll be fun” and the uni was born.
that looked cool. i want to try it now.