The province of Milan extended over the
Po Valley and was bordered by the
River Ticino to the west, and the
River Adda to the east. It was shaped by its waterways – river and canals that traverse it and sometimes border it, from the
Lambro and
Olona rivers to the numerous canals, like the Navigli Milanesi; these water runs link farmsteads and villages like Corneliano Bertario, the Castello Borromeo and ancient noble villas (such as the Inzago Villa near the Naviglio Martesana) to the Canale Villoresi, which is thought to be the longest man-made canal in Italy. The Villoresi is the natural southern border of Brianza, an area in Lombardy noted for its mountains, lakes and plains.{{cite web |work=ENIT - Italian National Tourist Board, MiBACT - Ministry for Cultural Heritage and Activities and for Tourism|title=Land Area and Persons Per Square Mile|url=http://www.italia.it/en/discover-italy/lombardy/milan.html It contains six regional natural parks: Parco Adda Nord,
Parco Agricolo Sud Milano, Parco delle Groane, Parco Nord Milano, Parco della Valle del Lambro and the Parco Lombardo della Valle del Ticino. Half of the province is agricultural and flood plain, and most of it is protected by reserves. ==Largest municipalities by population==