Olm
(Proteus anguinus)

Found in the underground cave systems of the Balkans, the Olm is a blind, cave-dwelling amphibian that has adapted so thoroughly to permanent darkness that it has lost its eyes entirely. It has developed extraordinary senses of smell, hearing, and electroreception to navigate. 

 

It also barely needs to eat — it can survive for up to ten years without food, and may live for over a century!