By Nick Parker, CNN
MEXICO CITY - Twenty years ago, the air in Mexico City was considered the worst in the world. It was so badly polluted that on one day, birds fell dead out of the sky.
Since then, the city has worked to clean up its act, but traffic remains a major problem. Streets are still clogged with carbon-emitting vehicles, but one new building can counteract the effect of 1,000 cars.
A striking building on the Mexico City skyline, the hospital tower also has a very unique feature: it "eats" smog.
The façade is coated in a special material, which when hit by sunlight's UV rays, begins to break down pollutants into less harmful substances. The designers say it neutralizes the effects of 1,000 cars a day.
Although pollution levels have declined, Mexico City is still grappling with being a megalopolis and the intrinsic problems it brings: there are some 4.5 million cars registered in the city, and that number grows by about 200,000 every year.
The genesis of the design began some 10,000 kilometers away, in Berlin.
"We were witnessing the rise of smart materials and their applicability in architecture. And what we saw was a city full of built structures which were essentially dormant. That had the potential to work with this atmospheric activity but currently weren't," said Allison Dring, co-director of Elegant Establishments.
Using a material called titanium dioxide, they developed a pigment that coats the tiles, or so-called modules. When pollutants come into contact with the modules, they're turned into compounds like water and carbon dioxide.
"The design is inspired by natural shapes. It's kind of similar in appearance to corals. There is a need in the photo catalytic reaction for a maximum surface area and the natural forms of corals for example are very good at doing that," said Daniel Schwaag, co-director of Elegant Establishments.
Mexico was the first country to commission the project as part of a $20 billion investment into health infrastructure. City environment officials are impressed.
"What we have to do as a government is develop the public policies that make these kind of bioclimatic designs obligatory and not voluntary," said Tanya Muller, environmental secretary for Mexico City.
For now, critics may ask what difference isolated buildings can make to a global problem.
"The new angle of this technology is that it does something positive right there and then. Whereas we think of sustainability on a global scale. Urban air pollution is very localizable. So it directly shields urban populations from urban pollution," said Schwaag.
And this, say the architects, is a model that can be applied to any city around the world.