Indeed, the world's largest waterfall lies beneath the Denmark Strait, which separates Iceland and Greenland. At the bottom of the strait are a series of cataracts that begin 2,000 feet under the strait's surface and plunge to a depth of 10,000 feet at the southern tip of Greenland—nearly a two-mile drop.

The largest "underwater waterfall" on Earth is the Denmark Strait Cataract, located in the narrow stretch of water between Greenland and Iceland. While it isn't a "waterfall" in the traditional sense of water falling through air, it is a massive underwater phenomenon caused by density differences between cold and warm water. The frigid, dense water from the Nordic Seas meets the warmer, less dense water of the Irminger Sea; the cold water quickly sinks beneath the warm water, "falling" over a massive ridge on the ocean floor. This "underwater waterfall" drops nearly 11,500 feet (3,500 meters)—which is more than three times the height of Angel Falls, the world's tallest land-based waterfall. This massive downward flow carries an estimated 175 million cubic feet of water per second, making it a critical driver of the "Global Ocean Conveyor Belt" that regulates the Earth's climate. While you cannot "see" it from the surface like a normal waterfall, its immense scale and influence make it one of the most powerful and significant geographical features in the world's oceans.