The Treehotel in Sweden is shaped like an alien saucer, not something you’d expect to see in a forest, which is exactly what the designer of the UFO tree house was intending. The Swedish forest is filled with other unique, exclusive tree houses including one with all-mirror walls, one shaped like a bird's next, and more. https://www.youtube.com/watch?v=wz5SSo1KtEU&t=4s
