In Dagestan one may find such a wonder - a shaft-sinking and tunnelling complex Robbins (USA) that overcame 5 km in the mountains?! It used to be a diversion tunnel 5,2 km long from the dam to the station. Water went
through the generator producing electricity. It was done for elevation changes for bigger station power. The first machine of such type in Russia was exactly here, at Irganaiskaya hydrostation.