In 1339, Siena decided to show off its political, artistic, and spiritual prominence by expanding the Duomo. Work had just begun when the Black Death killed more than half the city’s inhabitants in 1348, and the project ground to halt, never to be resumed—partly because it was discovered the foundations could not support the massive structure. The abortive new nave, part of the so-called “New Duomo,” now houses many of the church’s treasures, including the glorious-if-worse-for-wear statues by Giovanni Pisano that once adorned the facade and the 30 sq. m (323 sq. ft.) stained glass window made for the apse in the late 1280s; the nine colorful panels, beautifully illuminated to full effect in these new surroundings, depict the Virgin Mary, Siena’s four patron saints, and the four Biblical Evangelists.

Upstairs is the “Maestà” by Duccio di Buoninsenga, considered a masterpiece from the day the altarpiece was unveiled in 1311 and carried in a solemn procession from the painter’s workshop on Via Stalloreggi to the Duomo’s altar. As a contemporary wrote, “all honorable citizens of Siena surrounded said panel with candles held in their hands, and women and children followed humbly behind.” The front depicts the Madonna and Child surrounded by saints and angels while the back once displayed 46 scenes from the lives of Mary and Christ. In 1711 the altarpiece was dismantled and pieces are now in collections around the world, though what remains here shows the genius of Duccio, who slowly broke away from a one-dimensional Byzantine style to imbue his characters with nuance, roundness, and emotion.

The Facciatone, a walkway atop the would-be facade of the “New Duomo,” is the city’s second most popular viewpoint, with a stunning perspective of the cathedral across the piazza and sweeping views over the city’s rooftops to Siena’s favorite height, the Torre del Mangia towering over the Campo.