The fourth span was once dedicated to the Crucifixion. Since the early 19th century it was dedicated to St. Joseph.
Since 1830 the altar was completely redone on design by architect Giacomo Moraglia. It is a work of several artists: Giovan Battista Argenti from Viggiù dismantled the old altar and set up the new under direction of architect of the Fabbrica Melchiorre Nosetti. Argenti sculpted the balustrade too, which was designed by the new architect of the Fabbrica, Biagio Magistretti. But the main work is the group of St. Joseph with Jesus as a teenager by Pompeo Marchesi from Viggiù, the same neoclassical sculptor of the altar front, with the relief depicting the death of St. Joseph, and of the cymatium with Angels and the Eternal Father.
The lateral paintings are two temperas on canvas: on the left the Marriage of the Virgin by Gaudenzio Ferrari, on the right the Nativity by Bernardino Luini.
These paintings can be dated back to the third decade of the 16th century. They were the closing panels of the altar-piece of St. Abbondio in the opposite fourth southern span. They were dismantled in 1815.
The Renaissance banner of the Confraternity of St. Abbondio, with Bishop Abbondio between the saints Proto and Giacinto protecting confreres and sisters, is exhibited towards the main nave. The display-case was designed in 1901 by Federico Frigerio, the Como architect who would have then restored the façade of the cathedral before, and then the burned dome, too.
The altar of St. Joseph was originally dedicated to the Crucifixion, as shown by the keystone with the personified Moon with a sad face expression while it is obscuring the Sun. That is the image of the eclipse and an emblem of Crucifixion, during which the sun was obscured .
The altar was also dedicated to St. Pelagia
From this chapel comes the wooden group of the Crucifixion that we can admire in the last side chapel in the transept.
The owner of this altar was the Confraternity of Santissimo Crocifisso, then associated to that of the St. Corpo di Cristo and St. Abbondio and St. Sebastiano, at last all absorbed at the end of the 16th century in that of Ss, Corpo di Cristo.
In front of the altar there were two tombs for the confreres. The other parishioners were buried in the demolished church of St. Stefano.
In this altar the relics of half bodies of the holy Bishops Rubiano and Adalberto are kept, at first buried in St. Abbondio, then in the cathedral behind the altar of the Crucifixion. The other halves of the bodies were in the Dominican church of St. Giovanni Pedemonte, then relocated to the basilica of Ss. Annunciata of Como in the sarcophagus at the altar of the Virgin.
The first altar of St. Joseph was erected in the cathedral in the three years of French republican government (1803-1805), however not endorsed by Fabbricieri, who in that period lost power, while in the near church of St. Giacomo was temporarily desecrated and reduced to a stable by the French: there the altar was dedicated to St. Carlo in the chapel of the Charity. Then it was removed from the cathedral because it was too high and of Baroque style.
That altar was again set up in the church of St. Giacomo and it was dedicated to the Virgin.
We do not know what happened to the first statue of St. Joseph.