It was in the middle of the thirteenth century, during the long struggle for independence carried on by the republics of Lombardy and Tuscany against the Empire and the nobles, that some of the most durable and splendid public works were executed. The domes and towers of Florence and of Pisa were rising above the city walls, while the burghers who subscribed for their erection were staining the waves of Meloria and the cane-brakes of the Arbia with their blood. Lombardy, at the end of her duel with Frederick Barbarossa, completed a vast undertaking, by which the fields of Milan are still rendered more productive than any other pastureland in Europe. The Naviglio Grande, bringing the waters of the Ticino through a plain of thirty miles to Milan, was begun in 1179, and was finished in 1258. The torrents of S. Gothard and the Simplon, which, after filling the Lago Maggiore, seemed destined to run wasteful through a wilderness of pebbles to the sea, were thus turned to account; and to this great engineering work, as bold as it was simple, Milan owed the wealth that placed her princes on a level with the sovereigns of Europe. At the same period she built her walls, and closed their circuit with the sixteen gates that showed she loved magnificence combined with strength. Genoa, between 1276 and 1283, protected her harbours by a gigantic mole, and in 1295 brought the streams of the Ligurian Alps into the city by an aqueduct worthy of old Rome. Venice had to win her very footing from the sea and sand. So firmly did she drive her piles, so vigilantly watch their preservation, that palaces and cathedrals of marble might be safely reared upon the bosom of the deep. Meanwhile, stone bridges began to span the rivers of Italy; the streets and squares of towns were everywhere paved with flags. Before the first years of the fourteenth century the Italian cities presented a spectacle of solid and substantial comfort, very startling to northerners who travelled from the unpaved lanes of London and the muddy labyrinths of Paris.