cardboard tubes + box = hours of fun! We pieced together TP and paper towel tubes. Used marbles. The kiddo loved it and even still pulls it out to roll the marbles into a dump truck. He wont' let me toss any cardboard tubes now.
This would be so cute in a Lil Girls room, use Chalk Paint and paint a castle outline on the wall and the kids can draw in the windows doors ect. and for Boys do a castle w/ dragan, or track on the wall ect.