Commerzbank Headquarters, Frankfurt, Germany

The world’s first ecological office tower.Height: 300.1 meters

Cost to build:  US$414 million

Completion date: 1997 

Fast fact: There is no observatory or open area on top. The public can only get as far as the plaza level.
With the aid of a 50-meter mast, the Commerzbank Headquarters in Frankfurt soars past the 300-meter mark by a whopping 10 centimeters. The building is the tallest in Germany and second-tallest in Europe, for now. It will be surpassed by the Shard London Bridge in 2012.

Swimming against the tide marks it out for this list.

The Commerzbank Headquarters was the world's first so-called ecological skyscraper, making use of natural systems of lighting and ventilation and reducing energy consumption as early as 1997.

In contrast to Europe's conspicuous lack of grand skyscrapers, this building celebrates its rise above low-rise offices, making it not just a symbol of Frankfurt's economy, but of Germany's attempts to pioneer eco-architectural design. 

Overall structure

Essentially the Commerzbank tower is a hollow tube standing on one of its ends. The vertical loads are concentrated at the outer walls of the building with the intention that the structural footprint can be as large as possible.²This special shape is by law of nature very stable and is able to resist horizontal wind loads. But this tube had to be perforated by the large openings of the gardens and, of course, by the windows. The entire architectural concept is based on these four-storey-high openings which run from the façade to the central core of the building. Because of the spiral arrangement of the gardens, the construction remains constantly solid. To keep the gardens free from columns the vertical forces have to be moved to the corners of the triangular plan. For that reason the structure consists of two main elements, namely the corner columns and the eight-storey-high steel structures which span across the gardens.³These structures, which are bridge-like, have two main functions. On the one hand