Denmark Strait Cataract

The Denmark Strait is the name of the 300 km-wide waterway between Iceland and Greenland. It features the world's highest waterfall, the Denmark Strait Cataract – but it doesn't draw much touristic attention, as it is completely underwater.

It is 3500 meters high, and it's created by the fact that the water on the eastern side of the strait is much colder than the western side, causing it to flow down the underwater terrain. It is estimated that its flow rate exceeds 5 million cubic meters per second.