The town has two centres: "Città alta" (upper city), a hilltop medieval town, surrounded by 16th-century cyclopic defensive walls, and the "Città bassa" (lower city). The two parts of the town are connected by funicular/cable car, roads, and foot-paths. Parking spaces are very limited in the upper city. The upper city, surrounded by Venetian walls built in the 16th century, forms the historic centre of Bergamo.