The Portico of San Luca is one of the longest arcades in the world. The arcade is 3.5 km long and has 666 arcades. It connects the Porta Saragozza with the San Luca Sanctuary, on Colle della Guardia. The Sanctuary was meant to house a miraculous icon of the virgin. The arcade was meant to protect the icon as it was paraded up the hill. A yearly procession proceed from the church of San Pietro in the center of Bologna to the Sanctuary along this path. Originally the arches held icons or chapels erected by the patron family.