A cave called "EL SOTANO DE LAS GOLONDRINAS", San Luis Potosi, Mexico -
El Sotano de las Golondrinas, a.k.a Cave of Swallows, is located in the tropics of central Mexico. Its size is impressive, the beauty of delights, identity fascinating, attracted by a BASE jumper and cavers from around the world. It falls to the Earth’s interior to a depth of 1,220-foot (370 m). Deep enough to engulf Empire State Building!