Deep in the limestone caves of the Balkans lurks a creature of legend. The olm (Proteus anguinus) was once thought to be a baby dragon by locals after heavy rains washed it above ground. This pale, cave-dwelling salamander spends its entire life in darkness and can live more than 100 years, all while eating and moving as little as possible.

The olm has colorless skin and frilly red external gills behind its head. These are key adaptations for surviving in lightless, oxygen-poor water. It lives only in black subterranean waters of Central and Southeastern Europe, where it never sees daylight. In this constant darkness, eyes are useless. The olm’s eyes are undeveloped and hidden beneath the skin, making it completely blind, while its other senses grow more refined. Like many cave-dwelling species, it lacks skin pigment. If exposed to light, its skin can gradually produce melanin and darken over time.