Next I decided on the site and took photos from every direction. Peter Nelson recommends picking a site you can drive to, in order to bring in your construction materials easily. Ours was accessible only by foot path, but the splendid river view seemed the overriding consideration.  The trees should be of sufficient size to support the tree house--at least 8 inches diameter. Not all trees are a good selection--some, like aspen, lack sufficient strength. For reference, both Nelson and Stiles list the type of trees to use, and the type to avoid. We picked a stand of maple.