The Arena di Verona is a Roman amphitheater completed in 30 AD, making it older than the Colosseum in Rome. It is one of the best-preserved ancient structures of its kind. While many Roman arenas became ruins or quarries for stone, the Arena di Verona has been in continuous use for public spectacles for nearly 2,000 years. In 1913, it was inaugurated as an opera venue, and today it hosts the world-famous Verona Opera Festival. Because of its elliptical shape and stone construction, the acoustics are so excellent that singers do not need microphones to be heard by the 15,000 spectators. The outer ring of the stadium was almost entirely destroyed by an earthquake in 1117, but the inner 'ala' (wing) remains as a testament to its original three-story height.