In the 1900s, the Mexican government used its uninhabited islands to test its military weaponry (in other words, bombs). That doesn't happen anymore, but the legacy of those tests remain through a series of giant man-made craters and caves littered around the Merieta Islands.
This picture of one of those craters, which is making the rounds online, now serves as an underground beach off the coast of Puerto Vallarta, Mexico. Beautiful though it may be, we can't look past the fact that it's basically just a giant bunker, the kind that haunts you in your sleep. It's 80 feet deep, about double the size of Royal St George's infamous "Himalayas" bunker.