Some people may make fun of them, but as far as midlife crisis purchases go, adult treehouses beat all other micro-dwellings by a landslide. Far from the simple platforms redolent of childhood, the latest crop of inventive treehouses come in all shapes and sizes, and many were built by firms that exclusively focus on arboreal architecture. There are now treehouse churches, a growing portfolio of treehouse hotels, treehouse microbreweries, and even a treehouse-inspired facility for cancer patients. One man built his girlfriend a treehouse, and then proposed to her by carving "will you marry me?" onto the side of one of its wooden planks. Below, 15 treehouses that will make you doubt your desire to live on land.