A small jewel-box theatre hidden on the upper floor of the Palazzo Pubblico, with three tiers of gilt boxes and a frescoed ceiling. The original 16th-century theatre burned in 1742 and the present form is mostly 18th-century, but the space is one of the most atmospheric small theatres in Italy.
It still hosts opera and concerts during the Siena Music Weeks in summer; check the Accademia Musicale Chigiana programme for performances. Outside concerts, occasional guided visits are arranged through the comune.