The Palazzo della Ragione is located in Piazza dei Mercanti in front of the Loggia degli Osii. The building has a rectangular plan, with two aisles with arcades that describe a real covered square. The arcades consist of seven major arches in the sides and two smaller ones. From the porch you enter Piazza Mercanti through five steps which occupy the whole side. The upper floor has five large windows with three lights, plus a round-arched window with the relief of Oldrado Tresseno a commemorative plaque from building in his name. Its function was to broletto, the center of the city, since its construction in 1233 when it was erected, and was used until 1776. He then became the seat of the notarial archives during the reign of Empress Maria Theresa of Austria, and between 1866 and 1870 hosted the first branch of the Banca Popolare di Milano.