Discovered in the early 1900s by two Bermudian boys searching for a lost cricket ball, this ancient cave, which is fed by crystal-clear ocean water and covered in calcite, has inspired the likes of many, including Mark Twain, its supposed first tourist visitor. The tour you take to access it is fun, especially if you're in a small group: They turn the lights out for a second at the end to simulate the boy’s pioneer discovery, which is both surreal and nerve-racking.