The view from the future towers to the Prater is free from cars: The two towers with 90 and 120 meters height complete the mixed-use development, a car-free quartier with 100.000 m² called 'Viertel Zwei': The shorter tower with residential use, the taller one with offices and a hotel. The Client is IC Development. One of the key points of the comfort concept is to have winter gardens facing South as buffer zones to be used by the residents and to enhance natural ventilation. The taller tower has a naturally assisted ventilation: a central shaft not only supplies fresh air into the floor areas but is also used for exhaust air with the stack effect reducing the necessary fan power.