Siena, which 'til this day, retains its medieval character, sits on three hill tops, just over 320 meters above sea level, in the very heart of Tuscany. The buildings of the city are predominantly red brick with red tiled roofs. The entire city is encompassed within a square mile, so travelers can easily see and enjoy every corner. Neither cars (save a few authorized vehicles) or bicycles are permitted inside the city walls.
The three major attractions within Siena are the main public plaza - the Piazza del Campo - and the adjacent Palazzo Publico, with its museum, and three blocks west, the Duomo, one of the world's most beautiful cathedrals. During the over 200 years it took to build the Duomo, it was worked on by some of Italy's most reknowned artists including Pisano, Michelangelo, Pinturicchio, Duccio, Donatello and Bernini.
If you visit between July 2nd and August 16th, you will witness the Palio, a bareback horse race that has been run for over 800 years and still draws tens of thousands of spectators. The race is only 90 seconds long, but the festival gathers steam over the preceding days.
Originally an Etruscan outpost, it evolved into a Roman colony, founded by the Emperor Augustus, called Sena Julia. The Lombards gained dominion over the city during the middle ages, but they were supplanted by a succession of Carolingian counts. During the 200 or so years from the 9th to 11th centuries, the city was dominated by the church. In 1147 it became an independent city with an increasingly aggressive policy of expansion into adjacent territories.
Siena and Florence engaged in a 400 year long struggle for domination, driven by the competition between the Ghibellines and Guelfs. Siena defeated Florence at the Battle of Montaperti in 1260, but over time the Florentines regained their strength, and with their allies, the Spanish, laid seige to Siena, which fell in 1555. The city remained part of the Duchy of Florence until the unification of Italy.
The black death hit Florence in 1348, at a time when Siena, with a population of about 50,000 (equal to Paris or London), killing off more than three quarters of the population, and decimating civil rule and the local economy.
During the 14th Century, the city, with its steep, winding alleys paved with stone, was divided into the 17 wards or contrades, a municipal structure that remains intact. During the Palio, each contrade is represented by men and women in medieval costume, carrying the flags and standards of their neighborhood. Colorful is too weak a word for the display. Try amazing!
The innumerable cafes, pastry shops and other stores seem only to be seperated by the dozens of gothic palaces and many ancient churches scattered throughout the city. Step into the sanctuaries of these churches and you are likely to find unsurpassed alter pieces and other clerical treasures.
The Sienese Renaissance produced a gothic style distinctive to that of the Florentines. The works of its principle artists, Duccio, Martini and the Lorenzetti brothers are found all over the city.
Take your time - whether site seeing or shopping, or both. Siena is a treat. If you can, visit during the off season when you won't be as overwhelmed by tourists as you will be in July and August.
THINGS TO SEE
The Piazza del Campo, the unique shell shaped piazza at the centre of the city, and twice a year the racetrack for the Palio (q.v.).
The Palazzo Pubblico, Siena's City Hall for almost 800 years, contains (amongst many other things) the famous frescos on good and bad government by Ambrogio Lorenzetti, frescoes by Simone Martini and Duccio, and access to the Torre del Mangia, from whose top you can view a beautiful panorama of the Sienese countryside.
The Duomo, Siena's magnificent black and white Italian Romanesque cathedral including the Libreria Piccolomini, Baptistery (separate entrance and charge), and an attached Museo dell'Opera del Duomo (separate entrance and charge)  which includes the famous Maestà by Duccio. After you've seen all the art, you can also treat yourself to a beautiful panorama from Il Facciatone in the museum.
The Pinacoteca, full of Sienese painting from the city's Medieval heyday.
The Palazzo Salimbeni, built in 1472, is the world headquarters of Monte dei Paschi di Siena, the major banking corporation which has a hand in much of the economic and cultural life of the city. The building itself is well worth looking at from the outside. Inside, there are interesting documents showing the history of banking, plus a collection of paintings and other artwork, but you would have to request permission in advance if you'd like to have a chance to view them.
The house where St. Catherine of Siena was born is just a few blocks from the duomo. This 14th century mystic is one of the principal patron saints of Italy.
The Piccolomini Palace built in 1459 by the well-known architect Bernardo Rossellino, disciple of Leon Battista Alberti. The Piccolomini Palace is one of the most popular sites on the Piazza del Campo. The Florentine style palace is home to the official archives of Siena.
THINGS TO DO
Palio Horse Race - a horse race like nowhere else, between the 17 contrade of Siena, is run in The Campo of Siena in July and August . All Sienese are affiliated with one of the contrade, to which a typical Sienese feels loyal with a strength perhaps surpassed only by their loyalty to their family. Since the 11th century, the Sienese have conducted festivals every year where the contrade compete for renown (and in times gone by, actual political power) through contests such as flag throwing, horse racing and even fist fights. The fist fights no longer happen (a heavy police presence in the weeks prior to the contest sees to that), but the spirit of competition between contrade is still fierce. The race itself is in late evening but the whole day of the race is taken up with processions through the streets of the various contrade competing in the particular race (only ten can compete at any time for safety reasons).
Classical concerts during the summer at the Accademia Musicale Chigiana, and at various locations in the city during the Settimana Musicale Senese.
Siena Jazz Festival during summer.