"In 1869 the craftsman Rousseau of Marseilles built this monocycle, which perches the cyclist on the inside of a 2 1/2 yards-high wheel. As there is no steering mechanism, it makes uncommon demands on the rider's sense of balance." (from Galbiati & Ciravegna)
Cycling is already fun. Imagine, then, cycling and still be able to color the ground where you go? That was exactly the idea of the staff of the NY Studio Gelardi, Contrail with the design of public art. As you walk with your bike, the rear wheel is leaving a trail of chalk dust of various colors.