The three castles and the city walls of Bellinzona were built in medieval times; the reason these fortifications were built was to block access to the Ticino valley to northern populations and control tolls and roads to S. Gottardo. After reconstruction over the centuries, recent restoration and improvements the three castles, Castelgrande, Montebello and Sasso Corbaro appear in all their splendour and are the main tourist attraction of the city. In 2000, the Bellinzona castles received the recognition of "World Patrimony of Humanity" from UNESCO.