A majestic Douglas fir proudly lifts this stout abode twenty feet up its trunk. The treehouse serves as a retreat for a couple that lives in the cozy lake house below. A mere 12 feet square, the treehouse has a small outdoor deck and large windows that make it feel far bigger than it really is. Access comes from a stairway on the right side of the main house and a boardwalk that crosses the length of the roof.