Bats make their homes (roosts) in a variety of different structures. They can use trees, caves, cracks in buildings, bridges, and even the attic of a house!  The largest urban colony of bats in the U.S. lives under Austin, Texas' Congress Avenue Bridge during the summer.  The Congress Avenue Bridge becomes a temporary home to over 1.5 million Brazilian free-tailed bats! Watch this video of their emergence: