the bergmoench is an unusual bike design by koga which can be folded into a backpack. the bike is
designed to be compact and lightweight for climbing hills and mountains. the vehicle can be unfolded
into a bike at the top and ridden down the hill. the bike doesn't have pedals, relying on the slope of
the hill to propel the rider. it also doesn't have a seat, but does have foot rests and brakes. the idea is
users will climb a hill and roll down on the bike in a more upright position. the attached backpack
even has space for other things like a helmet  and food.

http://bergmoench.koga.com