The Estates Theatre is the best-preserved 18th-century opera house in Central Europe, and one of the few opera venues in the world little changed from Mozart's time. The neo-classical building opened in 1783 and hosted the premiere of Don Giovanni four years later, with Mozart conducting from the harpsichord.
The interior — cream and green, with tiered boxes and a painted ceiling — is arrestingly beautiful. The theatre stages opera, ballet, and drama today as part of the National Theatre complex. Attend a performance if the schedule allows; even a mediocre production is worth seeing in this space.