<p>Some of our planet’s most massive and difficult-to-reach caves are still in the process of having their secrets revealed. Take a look at a collection of the best photos of these extreme caves recently featured in <i>National Geographic</i>.</p> <p dir="ltr">Here, massive beams of selenite dwarf human explorers in Mexico’s Cave of Crystals, deep below the Chihuahuan Desert. Formed over millennia, these crystals are among the largest yet discovered on Earth.</p> <p dir="ltr"><i>—Brett Weisband</i></p>

Crystal (Un)clear Path

Some of our planet’s most massive and difficult-to-reach caves are still in the process of having their secrets revealed. Take a look at a collection of the best photos of these extreme caves recently featured in National Geographic.

Here, massive beams of selenite dwarf human explorers in Mexico’s Cave of Crystals, deep below the Chihuahuan Desert. Formed over millennia, these crystals are among the largest yet discovered on Earth.

—Brett Weisband

Photograph by Carsten Peter, National Geographic

Extreme Underground: 8 Best Cave Pictures

Head below the surface and get a glimpse into some of the world’s most spectacular underground caves.

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