Each spring, millions of Mexican free-tailed bats fly from under the Congress Avenue Bridge, but they weren't always welcome like they are today.

According to experts, Austin is home to the largest urban bat colony in North America. Approximately 1.5 million bats make the Ann Richards Congress Avenue Bridge their home for part of each year.

The Texas capital is now known as "Bat City," with a festival held each September on the Congress Avenue Bridge. Bats have also been deemed the state's flying mammal for the past 30 years. Austin ...