Commerzbank Tower, World's First Green Skyscraper

The Commerzbank Tower in Frankfurt-am-Main, Germany, was the tallest office building in Europe at the time and more significantly, the first green skyscraper in the world. This 850ft tall building is designed by Sir Norman Foster and partners between 1991 and 1997. Its centerpiece is the triangular atrium which houses "sky gardens" at 9 different levels, each featuring different types of vegetation (Mediterranean, Asian, etc.). Ahead of its time, the building design was unique and it incorporated novel environmentally-friendly technologies.

The building is triangular, comprising three 'petals' -- the office floors -- and a 'stem' -- the full-height central atrium. The sky gardens become the visual and social focus of the complex, providing places to meet others or to relax. The transparent central atrium also brings natural lighting to the inward-facing offices. Moreover, the building design also takes into account the prevailing winds and solar orientation, so that the building is naturally ventilated for 60% of the year. In this respect, the sky gardens also helps by being a natural ventilation. This approach would reduce the energy consumption of the building by close to 50% compared to an equivalent normal air-conditioned office.

The building kept on improving; most significantly, from 2008, the building has been supplied exclusively with green energy from naturally renewable sources. Currently it is still a very popular tourist destination in the city.