Presiding over the Piazza del Campo, this great Gothic-style town hall houses some the city’s finest artistic treasures. Siena’s medieval governors, the Council of Nine, met in the Sala della Pace, and to help ensure they bore their duties responsibly, Ambrogio Lorenzetti frescoed the walls with what has become the most important piece of secular art to survive from medieval Europe. His 1338 “Allegory of Good and Bad Government and Their Effects on the Town and Countryside” provides not only a moral lesson but also a remarkable visual record of Siena and the nearby country as it appeared in the 14th century. Probably not by accident, the good-government frescoes are nicely illuminated by natural light, while scenes of bad government are cast in shadow and have deteriorated over the years. In a panorama on the good side of the room, the towers, domes, and rooftops of Siena appear much as they do today, with horsemen, workers, and townsfolk going about their daily affairs; in the countryside, genteel lords on horseback overlook bountiful fields. On the bad-government side, streets are full of rubble, houses are collapsing, and soldiers are pillaging; beyond the walls, fields are barren and villages are ablaze.

Among other frescoes in these rooms is Sienese painter Simone Martini’s greatest work, and his first, a “Maestà” (or Majesty), finished in 1315 (he went over it again in 1321), in the Sala del Mappamondo. He shows the Virgin Mary as a medieval queen beneath a royal canopy, surrounded by a retinue of saints, apostles, and angels. The work introduces not only a secular element to a holy scene but also a sense of three-dimensional depth and perspective that later came to the fore in Renaissance painting. Mary’s presence here in the halls of civil power reinforces the idea of good government, with the Virgin presiding as a protector of the city. Just opposite is another great Martini work (though the attribution has been called into question), the “Equestrian Portrait of Guidoriccio da Fogliano.” The depiction of a proud mercenary riding past a castle he has just conquered was part of a long lost “castelli,” or “castles,” fresco cycle that showed off Sienese conquests.