Original photo by Ingrid Pakats/ Shutterstock

Waterfalls are some of the world’s most amazing wonders. Millions of people flock to these water-rushing giants — with names like Niagara, Yosemite Falls, and Iguaçu — to see them up close and in person. However, the largest waterfall in the world has no ticket counter, no gift shop, and no tourists. In fact, there’s nothing at all to see, because this waterfall is entirely underwater. 

The world’s largest human-made waterfall is more than 2,000 years old.

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At an impressive 541 feet, Cascata delle Marmore is an incredible display of Roman engineering. Although they may be known best for their impressive aqueducts, Romans were also in the waterfall-making business, and built this one in 271 BCE to redirect stagnant water to a nearby river.

Nestled between Greenland and Iceland is a body of water known as the Denmark Strait, and beneath its waves lies the world’s largest waterfall. Known simply as the Denmark Strait cataract (a “cataract” is a type of powerful, flowing waterfall), it cascades 11,500 feet toward the seafloor. This incredible deluge — like other underwater cataracts — is actually a dramatic dance between warm and cold water. In the case of the Denmark Strait cataract, cold water from the Nordic Sea meets the much warmer water of the Irminger Sea southwest of Iceland. The cooler, denser water sinks beneath the lighter, warmer water, dropping more than 2 miles to the seafloor. The resulting waterfall completely dwarfs Venezuela’s Angel Falls, the tallest terrestrial waterfall in the world, by more than 8,000 feet. The Denmark Strait cataract is also a staggering 100 miles wide, nearly 15 times wider than the widest terrestrial waterfall, the Khone Phapheng Falls in Laos, which is only 6.7 miles wide. By every single metric, this underwater avalanche towers over the competition — even though it never rises above sea level.

Numbers Don't Lie

Numbers Don't Lie

Width (in miles) of the Denmark Strait at its narrowest point
180
Year an enormous ice dam caused Niagara Falls to stop flowing for an entire day
1848
Number of waterfall types, including the punchbowl, plunge, multistep, horsetail, and cataract
10
Length (in seconds) of TLC’s 1994 hit “Waterfalls,” from their second album, “CrazySexyCool”
240

______ is the only waterfall that’s one of the Seven Wonders of the Natural World.

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Victoria Falls is the only waterfall that’s one of the Seven Wonders of the Natural World.

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The world’s largest volcano is also (mostly) under the ocean.

Some 590 miles northwest of Honolulu, a small, unassuming island known as Pūhāhonu (Hawaiian for “turtle rising for breath”) covers only a 5-acre expanse. But underneath the sea, Pūhāhonu is actually the very tip of the world’s largest volcano. Pūhāhonu is a shield volcano, a type of volcano named for its overall shape — which resembles a shield laying on the ground — and in 2020, scientists confirmed that its size surpassed that of the previous record-holder, Mauna Loa. At 36,000 cubic miles, it’s almost twice the size of Mauna Loa, which clocks in at only 19,200 cubic miles. Part of the reason Pūhāhonu remained such a well-kept secret is that nearly two-thirds of its bulk is below the ocean floor, and is covered by debris and broken coral. The volcano is so heavy, it has actually caused the Earth’s crust nearby to sink.

Darren Orf
Writer

Darren Orf lives in Portland, has a cat, and writes about all things science and climate. You can find his previous work at Popular Mechanics, Inverse, Gizmodo, and Paste, among others.