Few buildings in Italy stop you in your tracks the way the Cattedrale di Santa Maria Assunta does. Its façade — an extraordinary riot of white, green and red marble inlay — is one of the most extravagant in the world, begun in 1215 and worked on by the greatest craftsmen of the age for nearly two centuries.

The interior is just as arresting. The floor alone took over 600 years to complete and consists of 56 inlaid marble panels depicting biblical scenes and allegories — a Renaissance artwork you walk on. Above, the black-and-white striped columns rise to a gilded ceiling of deep blue and gold stars.

The Piccolomini Library inside the cathedral shelters a complete cycle of 10 frescoes by Pinturicchio (1502–1508), painted in colours so vivid they look freshly done. Nicola Pisano's great pulpit (1265–68) is considered the first piece of true Renaissance sculpture — predating Giotto, predating Donatello, predating everything.

The unfinished nave to one side was meant to make this the largest cathedral in Christendom — abandoned when the Black Death halved Siena's population in 1348, leaving a haunting shell that stands as one of the most poignant monuments to lost ambition in Italy.