Most cities use lots of regular old fashioned trees to help clean the air, but doesn't stop people from dreaming up higher-tech solutions. This giant concrete skyscraper from Czech architects Pavlína Doležalová and Jan Smékal is covered with pollution scrubbing algae, and is designed to create a chimney effect that sucks in hot polluted air at the bottom, purifying it before it finally gets released at the top.
The designers envisage several of these 800-ft structures positioned at strategic spots throughout a city, keeping the air clean and fresh. A built in irrigation system would keep the algae moist, held in place by the concrete spikes which they say are inspired by sea sponges.
Just how this works better than trees isn't clear to me. Here in New York City we have about one tree for every two people, so it would take a lot of these crazy algae towers to achieve the same thing. I guess the look is kind of interesting, but it also takes up a lot of valuable real estate.