Designers, too, seem to feel the allure of tree houses, often creating incredibly fanciful designs. A hotel in way-northern Sweden, located just 32 miles south of Arctic Circle, is tapping into this magnetism.

The husband-and-wife owners of Treehotel, Britta Jonsson Lindvall and Kent Lindvall, have enlisted six designers to create their fantasy modern treehouses. There's the 13-by-13 foot Mirrorcube, above, a reflective glass cube built around the trunk of a pine. It blends into the surrounding forest so well that the architects plan to cover it with a transparent ultraviolet film to alert flying birds, so they won't smash into it.

Here's the interior:

Here's an artist rendering of the 'Bird's Nest,' a cylinder covered in branches, designed by Inrednings Gruppen.

I love the idea of this 12-person "tree sauna":
The first four rooms opened in July; another two are slated to open this fall, including the aptly named UFO, shaped like a flying saucer.