Siena is a lovely medieval town, with the Piazza del Campo as its heart. We've visited Siena many times, each time discovering different streets and sections of the historical center, trying out new places to eat at.
What are the main things to see in Siena? The Piazza del Campo is at the very top of the list, but then you have many other choices as well! How about going into the Palazzo Pubblico, the red brick city hall that overlooks the Campo and visiting the Civic Museum? It holds a lot of treasures, including some of the most interesting, thought provoking frescoes on the role of government. How about climbing up the Torre del Mangia and looking down on all of Siena?
Head to the Piazza del Duomo and buy yourself a pass to visit the inside of the cathedral, the baptistery, the Museum of the Opera del Duomo from where you can enjoy another view of Siena, and the crypt. Inside the cathedral enjoy the beautiful pavement stories and the Piccolomini Library.
Enjoy the art of the Sienese masters? Head over to the Pinacoteca Nazionale di Siena, or the "picture gallery", for some more masterpieces by Duccio di Buoninsegna, Simone Martini and Pietro Lorenzetti, among others.
Also check out the Santa Maria della Scala in front of the Duomo. This is one of the first examples of "hospital" (as in hospitality) in Europe that welcomed pilgrims making their way to Rome. Today it is a museum and hosts many temporary exhibitions being held in Siena.
These are just some of the main sights, check out the articles below for more details and sights you should see while in Siena.