New home doesn't have a yard - what can I do with the deck for the kids to play?

We finally moved to a great area with great schools, but our new home doesn't have any yard. It does have a large safe deck they can use. (By safe, I mean, the deck area is built right onto the ground and completely fenced in). Does anyone have any ideas on what we can do with the space for our little ones to play in? I'm worried about jungle gyms where they might decide to jump off onto the wood. Right now they are 5 and 2. We have a small sandbox and play house so far, but I'd love to create a sort of adventure-land for them to call their own. via /r/Parenting http://ift.tt/2ohUhXM