Founded in 1773 by Gustav III (who was later assassinated here at a masked ball), the Opera House is the home of the Royal Swedish Opera and the Royal Swedish Ballet. The building dates from 1898. Performances are usually Monday to Saturday at 7:30pm (closed mid-June to mid-Aug). The box office is open Monday to Friday noon to 6pm (until 7:30pm on performance nights), and Saturday noon to 3pm.