A river rushing through an underground cave towards the sea

Here's what to know before you head to Rio Secreto, the massive underground river that flows beneath the jungle of Riviera Maya in Mexico’s state of Quintana Roo.

There are cave tours and there's Slovenia's Postojna cave system where you abseil into underground rivers in search of prehistoric beasts. Nick Redmayne braces himself

Puerta Princessa underground river is one of the unique landmarks in the Philippines. Within the Puerto Princesa park lies a hidden river, which flows underground and much of the park’s landscape sits on a limestone bed. The river runs through the limestone and directly into the sea, making parts of this subterranean river tidal.

Palawans Underground River

A 5-day trek through Hang Son Doong, the largest cave in the world. Located in Phong Nha-Ke Bang National Park in the Quang Binh province of Central Vietnam

Find out about the myth of a huge underground river flowing below Birmingham, Alabama. Discovered by serial hoaxer, Joseph Mulhatton in 1884

Beneath the bustling streets and historic buildings of Bologna lies a hidden world—an intricate labyrinth of tunnels that stretch out in all directions below the city. These subterranean passages have…

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