The Cave of Swallows

The Cave of Swallows, also called Cave of the Swallows is an enormous pit cave situated in a rainforest in San Luis Potosí, Mexico. The low point of the entrance provides a 1094 feet (333 m) freefall drop to the bottom of the cave while the high point provides a 1220 feet (372 m) freefall drop. The cave is known by the native name of Sótano de las Golondrinas, which means Basement of the Swallows, because of the large number of birds living in holes in the cave's walls. To free themselves from the cave, the birds fly in circles around the cave, gradually flying upwards until they are able to reach the surface and the sky.