Everyone has heard of rock climbing, but very few have heard of mattress climbing. Mattress climbing is inexpensive (if you already have the mattresses), it is fun, and it is perfect for all ages and most heights. The first three things you need to go mattress climbing are two mattresses and a wall. Once you have those it'll be easy, even for a baby, literally.
Take a mattress and place it against a wall either on its side or standing up. Either work, depending on the height of the person climbing. Once you have a mattress against the wall, place the other mattress in front of it. The mattresses should look like the picture below.
Climbing the mattress while it's on its side is really fun, but having it up the tall way takes mattress climbing to a whole new level. Seriously, can you imagine climbing a mattress? It is SO much fun that you won't want to stop.