Photo taken from Google-:
Bracaken cave, (in Texas, US) is the summer home to the largest colony of bats in the world. An estimated 20 million Mexican Free-tailed Bats roots in the cave from March to October making it the largest known concentration of mammals. The cave is located in southern Comal Country, Texas, outside the city of San Antonio. The 100-food-wide crescent shaped opening to the cave lies at the bottom of a sinkhole, formed when the roof of the cave collapsed.
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