America's Dirtiest Cities
No. 16 San Antonio
The Texas city has festive flea markets, barbecue, and a legendary old fort—and none of them are known for being pristine. The city didn’t budge from its slot since last year, but visitors can help prevent air pollution by exploring the city with one of the rented bicycles from the downtown B-Cycle program ($10 for a 24-hour pass, or first 30 minutes free then $2 per half-hour).