When you visit the Church of St. Ignatius of Loyola in Rome, you can contemplate the ceiling throug a mirror.

Andrea Pozzo painted it in XVIII century with a trompe-l'œil technique.

The ceiling is not a cupola, but it's flat.

https://video.nostr.build/f43441c0374c088f7888b0fadc02c3a1c9ead45c9b1b138657d62bf4a750247d.mp4