Congress Ave Bridge

Every year up to 1.5 million Mexican free-tailed bats make their home upon a platform beneath the Congress Ave Bridge. It's become an Austin tradition to sit on the grassy banks and watch as the bats swarm out to feed on the local insect population. Capitol Cruises, behind the Hyatt Hotel, offers bat-watching cruises on Town Lake below the bridge.

Locals are proud of this, the largest urban bat colony in North America. The colony, which is made up entirely of female and young animals, is at its most active when swarming out for the nightly feed. Such is the bat-density that bat-radars have detected bat-columns up to 10,000 bat-feet (3,050m) high. In June, each female gives birth to one pup, and every night at dusk, the families take to the skies in search of food. The spectacle of 1.5 million bats flitting forth at once looks a lot like a fast-moving, black, chittering river. It's become an Austin tradition to bring along a six-pack and cheer the bats as they head out to feast on an estimated 30,000lbs (13,500kg) of insects per night.

Bat Conservation International has volunteers on hand and holds programs throughout the bat season. Congress Ave Bridge crosses the Colorado at the southern end of downtown.