Hoyo Soplador (Blowhole)

When the waves are just right, this coral formation spouts seawater up to 20 meters into the air. The Hoyo Soplador also makes a thunderous sound as the water rushes through the narrow blowhole into the air. Since the blowhole is both easily accessible and free to visit, it's one of the most popular attractions in San Andrés Island in Colombia.

Part of what makes this natural wonder so special is its relative unpredictability. The wind and tides need to align properly in order to produce sufficiently powerful waves. Local business-owners tend to have a reasonable idea of when it'll go off, so it pays to ask around.