This giant natural cave is right below one of America's favorite theme parks (and yes, you’re allowed to explore it).

Bat colonies can reach truly enormous sizes, some with millions of bats pouring out to feed each night, and one cave in Texas has the largest of them all.

Also called "dikengyuan" in Mandarin, which means "pit courtyards," the homes are a type of cave dwelling ("yaodong") commonly found in the Loess Plateau in northern China. "Academic literature ...