Opera Garnier is Paris at its most theatrical: marble staircases, gilded foyers, ceiling paintings, and a grand auditorium built to impress before the curtain even rises. Charles Garnier's 19th-century opera house is still used for performances, but it is also worth visiting as architecture.
The self-guided visit is enough for most travellers. Look for the Grand Staircase, the Grand Foyer, and the auditorium ceiling painted by Marc Chagall, then step outside to see how the building anchors the boulevards around it.