Siena lies in the picturesque Tuscan hills south of Florence, which was throughout much of the city's history its chief competitor for wealth and power. Siena began to prosper in the 12th century and reached its artistic zenith in the 13th and 14th centuries, when its artists rivaled those of Florence. The cathedral and palaces of Siena, most of them built of brick made from the local red clay, are outstanding monuments of Gothic architecture. As you explore the many tourist attractions in Siena's beautiful Centro Storico, the historic old town, be prepared to do a lot of walking, most of it uphill - or so it may seem.