Ever since I read Swiss Family Robinson, as a child, I wanted to live in a tree house. My favorite spot to go was high up in the Dogwood tree that grew beside our old house in Wyckoff, NJ. I still love tree houses and climbing trees.
Glass igloos in Finland to sleep under the northern lights. Hotel Kakslauttanen's Igloo Village in northern Lapland. Their 20 glass igloos have thermal panes that keep the digs warm and prevent frosting.