The Medici, having conquered Siena in 1555, built this brick fortress to keep the city in check. It is a textbook Italian Renaissance star-fortification, with four corner bastions and a wide moat. The interior is now a large public park, popular for evening passeggiate, and the bastion walls give views over the western side of the city.
The Enoteca Italiana inside the fortress is a state-supported wine cellar with bottles from every region of Italy available for tasting — an inexpensive way to compare Brunello, Chianti Classico, and lesser-known Tuscan wines side by side.