Hesarek & Bingöl Mountains

Imagine immortality being as close as a lake… In some tellings of the Köroğlu tales, the water of life, the water of immortality, is said to lie hidden in one of the lakes of the Bingöl mountains. Whoever drinks it will live forever; but who it was that drank it is told differently in every version… So among a thousand lakes, how do you find the right one?