The oldest continuously active opera house in the world, opened in 1737 — predating La Scala by 41 years. The interior, all red velvet and gold tiers, is one of the most beautiful theatre rooms in Europe. Its acoustics and the quality of its productions have been renowned for nearly three centuries.
Book guided tours or evening performances well in advance. The opera season runs October to June; a ballet season fills the summer months. Even if you can't attend a performance, the 45-minute guided tour is worth it.