Bergamo is about 40km northeast of Milan. It is served by Orio al Serio International Airport, which also serves the Province of Bergamo, and to a lesser extent Milan. The foothills of the Alps begin immediately north of the town. The upper city, surrounded by Venetian walls built in the 17th century, forms the historic centre of Bergamo. The lower city, having expanded rapidly during the 20th century, is the modern centre of Bergamo.
