Clothesline tent combo // String a rope in your backyard. let the kids bring out a bedsheet & drape it over. weigh it down on the edges. Sprawl out a blanket. let them have their very own pincic & day play camp out!
Make Like a Montessori Mama: Part 4 - Shape Activities
Looks like someone else has also had the idea to create "Lincoln planks" for the kids to build with. A permanent installation like this could also work well in the right setting, doubling as outdoor seating as well as a balance course