This Adventure Playground in Berlin has it all; animals, soccer field, indoor gathering area, bicycle mechanic shop, art studio, and much more. The piece that I thought was amazing was the fort building area.
Kids rent a numbered platform for two weeks where they can build their own fort. Tools are rented on site. Old nails can be pulled from stacks of old boards and traded in for new nails. This also helps keep the grounds clean and safe(er).
Each fort is connected by a long series of elevated decks. In the summer there are overnight events where you sleep in your fort!