The day trips listed below are ones which will take an entire day and evening.  We often leave mid-morning and time our arrival for an early lunch, leaving us the afternoon to explore, and visit galleries and sites.  After a leisurely dinner, we drive back to il Mulino, and arrive between 10 pm and midnight.  We typically take one or two of these longer day trips each week, and concentrate on places nearby for short outings on other days.  This gives us a nice balance of activities and time to enjoy il Mulino as well. 
Florence is approximately 1.5-2 hours away.  It is a very do-able day trip.  Our favorite day out is to arrive for lunch, wander the city, visit the Uffizi Gallery and the Gallery of the Academy (David), followed by a glass of wine at a bar along the Arno, then dinner, gelato and the drive home. 
Rome can be reached in about 1.5 hours.  We often arrive mid-day to late afternoon and spend time around St. Peter's and the Sistine Chapel, or at the site of ancient Rome.  Following that, we enjoy wandering the various Piazzas, Spanish Steps, and often eat at the Piazza Navona, where many people are out to see and be seen. 
Siena, is also a very easy day trip, being about 1.5 hours away.  Enjoyable as a city to wander, it provides a picturesque, Gothic setting for photos.  Il Campo, where the famous horse races Palio di Siena) take place, is circled by restaurants, cafes and bars.
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