Step inside this massive cave labyrinth hidden under Borneo

Beneath the island’s rainforest, explorers search for new discoveries deep within some of the Earth’s largest, longest, and wildest caves.

At dusk, a swarm of bats disperses to hunt in the rainforest surrounding Deer Cave. One of the planet’s largest underground passages, it holds more than two million bats.

Late on a sweltering morning in April, two slim British cavers named Frank and Cookie lowered themselves into a slick, humid pit deep below Borneo’s rainforest.

Climbing down past an ancient heap of bird guano and pushing through a gallery of gleaming pillars the color of old bone, the pair were hoping to make history. They had crawled into Cave of the Winds, deep inside a cave system known as Clearwater, where they would search for a passage to Racer Cave, part of the Racer-Easter system.

Connecting the two would create a “super system,” one of the longest subterranean labyrinths on the planet. As the men wormed down, drilling and hammering bolts into the slick rock to hold their climbing ropes, their odds of success seemed good.

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