Mirrorcube by Tham & Videgard Architects

If you're in Sweden, check out the Mirror Cube, part of the Tree Hotel in Harads. The structure consists of light-weight aluminium and mirrored glass hung around a tree trunk. (I know what you're thinking: "Won't birds crash into the nearly invisible building??") Fortunately, steps were taken to prevent wildlife from crashing into the treehouse by applying transparent ultraviolet colour visible for birds only, into the glass panes. See more@ TVARK