Built to demonstrate the enormous wealth, proud independence and secular nature of Siena, this 14th-century Gothic masterpiece is the visual focal point of the Campo, itself the true heart of the city. Architecturally clever (notice how its concave facade mirrors the opposing convex curve) it has always housed the city's administration and been used as a cultural venue. Its distinctive bell tower, the Torre del Mangia, provides magnificent views for those who brave the steep climb to the top.
The municipal offices are closed to visitors, but the major historical sale (halls) and rear loggia now form the unmissable Museo Civico.