Who said that tree houses are only for kids and you cannot get creative when it comes up to building one.
Tree houses, or tree forts, are buildings constructed among the branches or next to the trunk of one or more mature trees, and are raised above the ground. Tree houses can be built for recreation or permanent habitation.
Check out these unusual tree houses that make you want to get one for yourself:
Also, here are couple futuristic tree houses to get your inspiration going.