Points of interest in Brugge are the more than 50 bridges that span the canals in the city and that can be opened to permit the passage of ships. Among the many medieval buildings in the city are the 13th-century Halles, or marketplace, with a belfry 108 m (353 ft) high; the Cathedral of Saint Salvator (13th-14th century); the 12th-century Chapelle of Saint Sang; the 12th-century Hospital of Saint John; the 13th-century church of Notre Dame, with a 122-m (400-ft) tower; and the Hôtel de Ville, the oldest town hall in Belgium, begun in the 14th century.