Interesting museum in Bala Klava, just before Sevastopol, when coming from Yalta.
There was the central base for submarines of the Red Fleet for the Black Sea.
A tunnel thru a mountain, subs could enter on one side of the mountain, being refueled and even repaired under the mountain, and leave on the other side into the sea.
Besides the museum itself, now it is a cozy village for holiday season. Well maintanined, because of completely closed village during Soviet times. The rich guys from Kiev have their yachts down there.