(Photo: Skidmore, Owings, & Merrill/Eduard Hueber)
When people are prompted to think about appealing architecture, they invariably consider New York City's subway system. This door is an example of why. The new entrance to the station at 560 Lexington Avenue in Manhattan features this lovely curved glass door.
Skidmore, Owings, & Merrill designed it to swing open and closed along a rounded track. It closes off the system at night, but permits people and pizza-encumbered rats to gaze and down to the platform below. You can see more photos at Contemporist.