When Alex (which one escapes my memory) suggested we go and check out an ex-Soviet underground submarine base on the Black Sea, I was curious but dubious about what we might find. My doubt was misplaced, and I was not disappointed.
After paying the equivalent for 50p, we were granted entry to the previously classified Russian submarine base. Large tunnels led from the cliff faces of the Black Sea deep into the hill of Balaklava. Inside, they spread out into a staggering underground network of waterways, tunnels, railways and supply depots, all serving the supply, rearm, and maintenance of the submarines that visited. The scale was amazing, and the entire complex buried deep enough to survive a direct hit with an nuclear impact, with feet thick blast doors able to seal off all access to the world outside.