Big European cities go green

This year, the English city of Bristol was named the "European Green Capital." Every year the European Commission awards the title to the European city that best combines environmental protection, economic growth and quality of life. Green spaces and water make up one-third of the city, and 25 percent of Bristol's homes were made energy-efficient over the last 10 years.

Since 2012, tropical forest has been gracing the Berlin Dussmann House. The vertical garden "Mur Végétal" (vegetal wall) was created by the French botanist Patrick Blanck. More than 6,000 tropical plants bloom and expand over a 270-square-meter (2,906-square-foot) wall. It all works with the help of a clever irrigation system. Blanck does not use dirt.

The green house in the Hamburg neighborhood of Wilhelmsburg opened in April 2013 on the occasion of the International Architecture Exhibition, and is the first of its kind. Since then, the glass façade merrily gurgles along. Two sides of the building contain water-filled glass elements where algae grows and produces energy for the house.

And now for something completely different: London's Green Roof Map (click on + on the top right). Roughly 700 green roofs that span 175,000 square meters (or 25 soccer fields) are depicted in this interactive map. The location and description of a particular roof garden - for example gardens for walking, vegetable gardens and roof cafes - can be seen online.

The forest spiral is a residential complex completed in 2000. It is a signature building from Viennese artist Friedensreich Hundertwasser. Space for "tree residents," or trees that grow out of the windows, was planned alongside about 100 apartments. The trees aren't only nice to look at - they also provide oxygen and a more pleasant city climate.

Antoni Gaudí's Park Güell was commissioned by industrialist Eusebi Güell and built between 1900 and 1914. Gaudí designed a garden city with more than 60 villas - but the park was never completed, as financing fell through. What remains is Güell's home - today a school - Gaudí's home, a museum since 1963, and the home of an architect friend that remains inhabited today.

It was an elaborate construction project, and now it's an elaborate park - an 8-kilometer (5-mile) green space directly along the Manzanares River. For that, highways were relocated underground, countless trees were planted, and a total of 33 pedestrian bridges were constructed or restored. The Arganzuela Bridge, pictured here, is especially worth the trip - day or night.

The René-Dumont green belt in Paris is in a park constructed on a former train track. Train travel was halted in 1965, after which a pedestrian promenade was built. Worldwide, this was the first elevated train route converted to a greenway. The better-known High Line in New York, shown in this picture, opened in 2009 and is based on the French park.

Nantes, France's sixth-largest city, was Europe’s "Green Capital" in 2013. Especially noteworthy is the botanical garden in the city’s center (pictured above) or the many snack gardens - "stations gourmands" - throughout town. Here, anyone can harvest strawberries, cherries, tomatoes, apples or whatever happens to be growing. The European Green City for 2016 is Ljubljana.