Divers Have Discovered the World’s Longest Underwater Cave

When exploring new corners of the globe, the common wisdom is to “dive deep,” but rarely is that advice literal. Now it is: A team of divers in eastern Mexico have discovered what’s believed to be the longest underwater cave in the world, just three miles west of the white sand beaches of Tulum.

The findings confirm that the vast, 164-mile-long Sistema Sac Actun, a waterlogged system of natural sinkholes, or cenotes, is actually connected to the nearby 52-mile-long Dos Ojos system, bringing the total length of the caves to a winding 216 miles. That’s more than the combined height of 24 Mount Everests stacked on top of one another. The warren of caves also stretches downward, to a depth of more than 332 feet, making parts of it deeper than London’s Big Ben is tall.