Aha! I have it! The grand foyer of the Palais Garnier opera house in Paris. It was only with the help of an internet search that I could confirm my own ever so treacherous memory. So it is that I toss my own photo on top of the enormous stack of extant photos of that grand foyer.
I shall not, however, contribute anything about my own experience of the flimsy nature of human memory. A bibliography of great works of literature that already address that theme would be enormous, also.