The Venetian Lagoon stretches from the River Sile in the north to the Brenta in the south, with a surface area of around 550 square kilometres (210 sq mi). It is around 8% land, including Venice itself and many smaller islands. About 11% is permanently covered by open water, or canal, as the network of dredged channels are called, while around 80% consists of mud flats, tidal shallows and salt marshes. The lagoon is the largest wetland in the Mediterranean Basin