4. Siena's Cathedrale di Santa Maria, better known as the Duomo, is a gleaming marble treasury of Gothic art from the 13th and 14th centuries. History Siena's Duomo was built between 1215 and 1263 and designed in part by Gothic master Nicola Pisano. His son, Giovanni, drew up the plans for the lower half of the facade, begun in 1285. The facade's upper half was added in the 14th century.