I have a screen shot of a tent with tables, food and candles with hanging red roses.
I have setup a wide screen monitor and wanted to do another screen shot at the
increased resolution. As my screen shot has the mini map shown, I was able to identify
its exact location, from "The grand place" marker, walk south through the alley to
an open courtyard. That is where it was but it is no longer there.
Strange indeed.

Seems to me like it was an event tent: food, candles, red roses? Not your everyday eating place. But I still don't know where the hell you're talking about.

Toussaint, between Cooper's Gate marker and Nilfgaardian Embassy marker.

Check the mini map on my image.

Ok, but those aren't roses (look like some kind of Hibiscus maybe). Nitpicking aside, it could still be an event setup. Can't say that I've ever noticed it in-game.

OK. Red flowers. The mini map is pointing north so it was easy to look for other possible locations on the map.
I even checked out the Novigrad map in case I was mistaken but there is no other possible location.

UPDATE: Through a gap in the tent's roof I could see a part of a blue and white building in the background with a yellow wall adjacent. I went back to the location and drew a sketch of the details that were visible and they match. There now stands a large statue where the tent was situated.