Main Tower

Frankfurt takes pride in ranking high on lists of the world’s most sustainable cities, and you can find an example of its energy efficiency at the Main Tower. Standing 200 meters (or 650 feet) tall, the building has 2,550 windows that can be opened outwards to circulate air and avoid the installation of a complete air-conditioning system. In 2011, the building received a LEED Gold certification for sustainability, the first existing German high-rise to receive the award that year. Other attractions in the building include a restaurant, lounge and Europe’s highest fitness club. In less than a minute, the building’s elevator takes visitors up to the observation deck for panoramic views of Frankfurt from the 56th floor—or one can walk up the nearly 1,100 steps, if a little exercise is in order.