With a length of 150 mi, Arno is the largest river in the region.
Arno river originates on Mount Falterona in the Apennines and flooded Florence regularly in historical times. It crosses Florence, where it passes below the Ponte Vecchio and the Santa Trìnita bridges. Sometimes, Arno river has a torrent-like behavior and it can go from almost dry to flood in a matter of days. New dams built on Arno river upstream of Florence provide protection now. The most famous bridge is Ponte Vechio. The bridge spans the river at its narrowest point where it is believed that the original bridge was first built in Roman times. It has always hosted shops and merchants who displayed their goods on tables, in front of their shops. Butchers originally occupied the shops. The present tenants are jewelers, art dealers, and souvenir stores. During World War II, Ponte Vecchio was not destroyed by the Germans during their retreat in August 4, 1944 apparently because of an express order by Hitler.
In 1565, Cosimo I de Medici had Giorgio Vasari build the Vasari Corridor above the bridge to connect Palazzo Pitti with the Florence’s town hall, Palazzo Vecchio. To increase the prestige of the bridge, at the end of the 16th Century the Medici Grand Dukes prohibited butchers but allowed the gold merchants to sell there. The bridge is also popular for lovers. It is said that by locking the padlock and throwing the key into the river, the lovers become eternally bonded.