Far underground in New Mexico’s Carlsbad Cave system, scientists have discovered drug-resistant microbes, according to National Geographic, which reports that the bacteria coated the walls of a cave 1600 feet below the surface.

The discovery took place in Lechuguilla cave, one of the world’s largest and deepest caves with more than 130 miles of passage.  The finding intrigues medical scientists who are studying  “superbugs.”

Read more: Drug-Resistant