An olm, also known as the Proteus or the cave salamander, is a unique and enigmatic amphibian species found in the underground caves and waters of the Dinaric Alps in southeastern Europe. It is famous for its unusual appearance and fascinating adaptations to its subterranean habitat. Some key characteristics and facts about the olm include:

1. Appearance: Olms are elongated and slender with a pinkish-white or pale, almost translucent, skin. They lack pigmentation and have small, underdeveloped eyes covered by a layer of skin, making them essentially blind. They typically reach lengths of 20 to 30 centimeters (8 to 12 inches) but can grow larger in some cases.
2. Adaptations: Olms have evolved several adaptations to their cave-dwelling lifestyle. They have sensory organs for detecting chemicals and vibrations in the water, which help them navigate, find prey, and communicate with each other in the dark, underground environment. They are also known for their slow metabolism and the ability to go without food for extended periods, sometimes several years.
3. Habitat: Olms are primarily found in underground karstic caves and aquatic systems, where they live in cold, flowing underground waters. These caves provide a stable and relatively constant environment, which helps them survive in the absence of light and extreme conditions.
4. Diet: Olms are carnivorous and primarily feed on small aquatic invertebrates like crustaceans, snails, and worms. They are skilled hunters and use their sensory organs to locate prey in the dark.
5. Reproduction: Olms have a unique reproductive strategy. They lay eggs, and the female guards them until they hatch. The hatching larvae have external gills, which they eventually lose as they develop into adults. Olms have a slow rate of reproduction, with females only laying a few eggs at a time, and they have a long lifespan, potentially living for several decades.
6. Endangered Status: Olms are considered a vulnerable species due to their limited habitat range, sensitivity to environmental changes, and the threat of habitat destruction. Conservation efforts are in place to protect their underground habitat and ensure their survival.

Olms are of particular interest to scientists and researchers due to their extreme adaptations to life in subterranean environments and their status as one of the few cave-dwelling vertebrates in the world.