Cave explorers discovered a pit inside a mountain range in central Croatia believed to have the world's deepest subterranean vertical drop, at nearly 1,700 feet, a scientific institute reported Monday.

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At the foot of the Velebit cave are small ponds and streams, including one of the largest known colonies of subterranean leeches, Sutlovic Baksic said.

Explorers find world's deepest hole

It's the cradle of Shangri-la, and one of the deepest river gorges on earth. It's a fortress guarding sacred waterfalls, and a cauldron of savage whitewater and unrunnable rapids. In the chill of the Himalayan winter, seven world-class kayakers led a massive expedition into the shadowy realm of Tibet's Tsangpo River , and launched their boats down its roaring throat. They were either going to die—or emerge transformed.

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