Siena, built on three hills and surrounded by well preserved walls, is filled with fine examples of Gothic architecture. It has one of the world's most unique piazzas "Piazza del Campo", shaped like a shell with scalloped edge. The "Palazzo Pubblico" (Town Hall), built between 1297 and 1342, with its famous "Torre del Mangia" forms one of the sides of Piazza del Campo. The Tower, 102 meters high, gives eccellents views over Siena and surrounding countryside. The Duomo or cathedral is a beautiful building, a mix of Gotich and Romanesque architecture with dark green and white marble. It contains, as Palazzo Pubblico, works by many artists, including Donatello, Pisano and Duccio di Boninsegna