Jumping platform

A Jumping platform is a naturally occurring or human-made surface for people to jump from. It is usually situated above sufficiently deep water, or above mats, a box-spring mattress, piles of empty cardboard boxes, or other soft landing surfaces, or they may be used together with other means of dampening the impact (such as for example, platforms for bungee jumping). Children often improvise platforms, either on a large scale (at abandoned quarries) or on a smaller scale (e.g. by moving a desk next to a bed, to jump onto the bed from the desk).

https://en.wikipedia.org/wiki/Jumping_platform