Mexico City

Once a week, car-flooded streets convert into bike- and pedestrian-flooded public parks in crowded Mexico City.

Air pollution is so bad in Mexico City that residents have less sensitivity to smells, according to a recent study.

With one of the world's higher rates of air pollution, Mexico City is cracking down on one type of emission: cigarette smoke. Smoking has been banned in all public places in the city, including office buildings and restaurants.

A look at the similarities between Los Angeles and Mexico City.