A secret marine residence

Hi! Interested and reading the internet things related to the former socialist residence "Pearl"I came across this property. I have no idea what exactly this property is, but it is interesting to me, because as one can see, it is unique – unique, and also obviously, the road to it starts exactly from a place that has not been very very hard guarded so long ago. This is not in any case "accidentally" place. From the satellite photos it looks maintained. Whether this property served the party and its purpose was to be even more hidden, or is it another strange jewel of some of our barber …? I wonder if anyone knows something to share it? 🙂 (people working on the beach around the residence know nothing, I already tried to ask a few of them)