Garnier, the older of the two Parisian opera houses, was the setting for the “Phantom of the Opera.” But today, it mostly features ballet performances. Whether you’re climbing the spectacular marble stairs or sauntering through the breathtaking foyer, this place is all about seeing and being seen, as it’s always been. Even the performance hall is sublime, with its almost 2,000 seats, traditional proscenium stage, and brightly colored ceiling fresco by Marc Chagall.