When we were looking for a house to buy he REALLY wanted one with a tree house, but that didn't work out. And while we have several trees, none of them are really suitable for a tree house. Next best option: a raised platform, a simple structure that will be adaptable and expandable.
This corner of the yard held a trampoline before we moved in, and there hasn't been grass there for years. Perfect for a fort. The top part will be a platform, with a railing around. Avery would like a ladder and trap door, a zip line, Miles wants a slide and a steering wheel. I'd like to enclose the bottom for a little play house, or make a giant metal-pipe-banging-chime thing. We'll see. That's the beauty of a simple structure- it can become what we want it to be. First things first, though- Concrete footings, a floor up there, a railing and a ladder.