Genoa centre of ancient origin, Pisa was already an important port in Roman times, definitively asserting itself as a seagoing power in the 12th century when it became a Republic after participating in the First Crusade. It extended its influence over the whole Tuscan coast and Sardinia, succeeding in defeating its rival Amalfi and the Saracens. This period was the start of the town's phase of greatest economic prosperity and artistic splendourCampo dei Miracoli (Piazza Duomo), one of the most famous sights in Italy and the world. Here lies the Duomo (11th-12th century), one of the major examples of Romanesque-Pisan art, with five aisles and housing important works of art such as the pulpit by G. Pisano (early 14th century) The river Arno flows pretty much through the middle of Pisa. The airport and the railway station are to the south of the river, with the bulk of the 'sights' being on the north side.