Venice hardly counts among the most-polluted places in the world. There are no cars traveling its narrow streets, and all traffic is either by foot or by boat. So despite the crowded walkways and canals, the air in Venice is far cleaner than that of, say, Milan, Italy's economic capital, which recent figures indicate has some of the worst air quality in Europe.
Even so, visitors to the Italian Pavilion of the architecture exhibition in the Venice Biennale, which will remain open until Nov. 19, will get a breath of fresh air. That's because parts of the concrete walls and grounds have been built with cement containing an active agent that, in presence of light, breaks air pollutants such as carbon monoxide, nitrogen oxide, benzene, and others through a natural chemical process called photocatalysis.