Congress Bridge Bats

A million winged mammals wake up and head out for dinner
Noteworthy for: The sheer spectacle of 1.5 million bats emerging from the underside of a downtown Austin bridge will amaze even those who don't know a bat from a basketball.

Just before sundown from March to October, throngs of Mexican free-tailed bats crawl out of tiny crevices under the Congress Avenue bridge and fly eastward for their nightly bug feast. The bat exodus over Lady Bird Lake looks like a horizontal ribbon of black smoke stretching into the distance.
A wide sidewalk on the bridge allows spectators to watch the bats from overhead, while others bring blankets and observe from the hillside just below the bridge. But don't get too close to the point where they emerge, or you may find yourself spattered with guano and bat pee.

The bats moved in soon after the structure was built in 1980, after discovering that the spaces between the expansion joints in the bridge were just the right size for bat hangouts.