Water wall Love this. Also like the idea of something that is changeable.more flexible. But using wood is appealing and the water stays against the "wall" so it has the thrill of movement w/o getting children very wet. That's appealing.
TeePee sand box from bamboo poles lodged in a tractor tire, tied together at the top, then draped with a sheet or canvas material. How fun! My nephews would love this! from Irresistible Ideas for Play Based Learning.