More ideas from fdm
Ramp out of cardboard tubes.

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.

A town for Lego toys to populate. | 31 Things You Can Make With A Cardboard Box That Will Blow Your Kids' Minds This would be fun for the last week of school.

Another pinner: Big box town! I remember doing this as a kid. Except, I used to draw ovens, ironing boards and tv sets. I Used to sit in them, out in the yard for hours.

DIY Sand and Rock Box

DIY Sand and Rock Box by FSPDT. Gdjk -> made this with toilet rolls (aka tunnels) and moon sand instead of play sand. My son loved playing with it. The moon sand cleans up nicely indoors but play sand will be easier to play with when using the small cars.