Countless caves perch atop the steep-sided mountains of East Kalimantan in Indonesia, on the island of Borneo. Draped in stone sheets and spindles, these natural limestone cathedrals showcase geology at its best. But tucked within the outcrops is something even more spectacular: a vast and ancient gallery of cave art.

Hundreds of hands wave in outline from the ceilings, fingers outstretched inside bursts of red-orange paint. Now, updated analysis of the cave walls suggests that these images stand among the earliest traces of human creativity, dating back between 52,000 and 40,000 years ago. That makes the cave art tens of thousands of years older than previously thought.

But that's not the only secret in the vast labyrinthine system.

In a cave named Lubang