Kinderpendent has a great tutorial on how to create a multi-layered cardboard garage.
Good for ages 10 and up.
Get the instructions here:
http://kinderpendent.blogspot.ca/2011/04/cardboard-parking-deck-tutorial.html
B inspired mama has a simpler garage, but numbers each spot and the matching car for number recognition practice.
Get the instructions here:
http://b-inspiredmama.com/2013/08/numbers-game-car-parking/
Lilla a design maker her version from a shoe box that opens up to have more parking spaces on the top.
Get the instructions here:
http://lilla-a-design.blogspot.com.au/2010/01/skolads-hus.html
Handmade charlotte uses an empty pizza box and toilet paper tubes to make a two story garage.
Get the instructions here:
http://www.handmadecharlotte.com/recycled-pizza-box-car-garage/