
The over 600 arches of the portico, unique in the world for its length of almost four kilometers (3,796 m), connect the sanctuary to the city and provide shelter for the yearly procession that since 1433 leads the Byzantine Madonna and Child to the cathedral in the city centre during the Ascension week. Its construction began in 1674 with the building of the Bonaccorsi archway by G. G. Monti over Porta Saragozza.