The Palais Garnier, renowned for its connection to the 'phantom of the opera', is an exquisite opera house built by Charles Garnier, a 35-year-old architect, in 1860. Take a 90-minute guided tour in English, or explore on your own with an audioguide (€5). Be sure to take in the magnificent Grand Staircase and the auditorium, adorned with red velvet seating, a chandelier and the colorful ceiling fresco painted by Marc Chagall. The museum, showcasing posters, costumes, backdrops, original scores and other memorabilia, is also worth a visit.