River Arno

Arno
View of the Arno from the Ponte Vecchio
Country	Italy
Basin features
Main source	Mount Falterona 1,385 m (4,544 ft)
River mouth	Ligurian Sea
Basin size	8,228 km2 (3,177 sq mi)
Physical characteristics
Length	241 km (150 mi)
Discharge	Average rate: 110 m3/s (3,900 cu ft/s) (at the mouth)

The Arno is a river in the Tuscany region of Italy. It is the most important river of central Italy after the Tiber.

The river originates on Mount Falterona in the Casentino area of the Apennines, and initially takes a southward curve. The river turns to the west near Arezzo passing through Florence, Empoli and Pisa, flowing into the Tyrrhenian Sea at Marina di Pisa.

With a length of 241 kilometres (150 mi), it is the largest river in the region. It has many tributaries: Sieve at 60 kilometres (37 mi) long, Bisenzio at 49 kilometres (30 mi), and the Era, Elsa, Pesa, and Pescia. The drainage basin amounts to more than 8,200 square kilometres (3,200 sq mi) and drains the waters of the following subbasins:

It crosses Florence, where it passes below the Ponte Vecchio and the Santa Trìnita bridge (built by Bartolomeo Ammanati but inspired by Michelangelo). The river flooded this city regularly in historical times, most recently in 1966, with 4,500 cubic metres per second (160,000 cu ft/s) after rainfall of 437.2 millimetres (17.21 in) in Badia Agnano and 190 millimetres (7.5 in) in Florence, in only 24 hours.