Absolutely, Siena is one of the most popular and feasible day-trip destinations in Tuscany, especially if you are based in Florence. Located only about 50 miles south of Florence, you can reach Siena in approximately 75 to 90 minutes by bus or train. Many travelers prefer the "Sita" bus (the corse rapide) because it drops you off in the upper part of the city near the historic center, whereas the train station is located at the bottom of the hill, requiring an extra bus or series of escalators to reach the sights. A day trip provides ample time to visit the stunning Piazza del Campo, where the famous Palio horse race is held, and the Siena Cathedral (Duomo), which is often considered one of the most beautiful Gothic churches in Italy. You can also climb the Torre del Mangia for panoramic views of the Tuscan countryside and enjoy a leisurely lunch of local pici pasta in one of the medieval side streets. While staying overnight allows you to see the city after the day-trippers leave, the compact nature of Siena’s historic core makes it very easy to cover the primary cultural landmarks between the hours of 10:00 AM and 6:00 PM.