BBI-Infotower at Capital Airport in Berlin, Germany; 102 feet tall; designed by Kusus + Kusus Architekten; A massive reinforced concrete elevator core carries the weight of the entire structure, allowing the exterior envelope to have a feeling of delicacy and lightness. Steel spiral stairs cantilever off the core with intermediate landings, and a view through the semi-transparent envelope. At the top are two observation decks, an encased platform and an open deck. - photo by Schwarz