I visited Moscow in July 2014, and during a stroll around VDNKh (a strange hybrid between an exposition ground and an amusement park), I came across the Buran spacecraft, the Soviet Union’s equivalent to the Space Shuttle and strikingly similar in design to its American counterpart. It wasn’t clear to me whether the specimen I saw was a mock-up or an original; it wasn’t possible to enter.
Since then I’ve wondered what exactly it was that I saw. The Wikipedia page on the Buran programme said that the actual spaceplane was destroyed in a hangar accident in 2002. I found this news site which indicates that the one I saw had probably been moved from Gorky Park, another area in Moscow, to VDNKh very shortly before my visit, and called the thing that has been moved “a life-sized prototype”. I also found this news site from 2000, which implies that the one installed at Gorky Park was one of a dozen “training vessels”; it looks like that would be the one that I would see in the other location fourteen years later.
So I’m pretty confident that the one I saw has never actually flown in space, but I wonder how much less than that it was. Was it a mere mock-up without any functionality at all? How close would it have been to the one that flew?
Perhaps it was a counterpart to Enterprise, a shuttle prototype only capable of atmospheric flight launched from a larger plane for test landings.
ETA: Apparently that craft has been at a museum in Berlin since before your visit to Moscow.