What's the largest waterfall in the world?

Even our tallest buildings can't rival the staggering size of the world's most iconic waterfalls, which include Niagara Falls on the U.S. border to Canada, Victoria Falls in Zimbabwe and Zambia and Angel Falls in Venezuela.

But which of these is the world's largest waterfall?

Angel Falls is the tallest waterfall on land, measuring 3,212 feet (979 meters) high and 500 feet (150 m) wide at the base, which is similar in size to three Eiffel Towers stacked on top of each other.

But technically, Angel Falls is not the biggest waterfall on Earth. That honor goes to the Denmark Strait cataract, a plunging water mass in the Denmark Strait — an ocean channel between Greenland and Iceland — meaning the world's biggest, tallest falls are underwater.

This is possible because of the temperature and salinity gradients that power most ocean currents, according to Anna Sanchez Vidal, a professor of marine Science at the University of Barcelona in Spain. The Denmark Strait straddles the Arctic Circle and acts as a funnel for polar waters flowing from the Nordic seas into the Atlantic Ocean. But like elsewhere in the ocean, the waters in this region aren't homogeneous. 

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North of the Denmark Strait, surface waters that come into contact with the frigid Arctic air cool and become saltier as some of the water freezes, leading the salt to be concentrated in the nonfrozen portion. Cold, salty water is denser than warmer water and therefore sinks to the seabed, while the balmier layer rises to the surface. This exchange fuels a deep, icy current flowing southward through the strait and into the Irminger Sea in the North Atlantic Ocean.