The Congress Avenue bridge spans Lady Bird Lake in downtown Austin and is home to the largest urban bat colony in North America. The colony is estimated at 1.5 million Mexican free-tail bats. Each night from mid-March to November, the Congress Bridge Bats bats emerge from under the bridge to blanket the sky as they head out to forage for food. This event has become one of the most spectacular and unusual tourist attractions in Texas. The most spectacular bat flights are during hot, dry August nights, when multiple columns of bats emerge. There are several points from which to view the Austin bats emerge and an information kiosk is located on the north bank of the Lady Bird Lake, just east of the bridge.