Museum of Military History (Maybe. Possibly.) in Budapest (Definitely).
I’m a bit vague about what this building is. My photo is named “rooftops castle.jpg”, very helpful (not!), but when I tried to confirm online that it is the castle, well, it looks nothing like the castle! Then I added “roof” to my search and countless images of the St Matthias church and its amazing tiling appeared — but, sadly, they don’t match this tile pattern (and you’ll notice there are no crosses at the top of this building). But it does seem to match the Museum of Military History.
All I can say for certain is that this is a building in Budapest and it has an amazing roof.
@Becky, this is like your quest to identify the Greenwich Foot Tunnel!
June Squares: Roof If you have a photo (or two!) of a roof, join in!