The ancient baptismal church, built around the eleventh century and raised to the rank of cathedral in 1462 by Pope Pius II, was given the title of Santissimo Salvatore (Most Holy Savior) because it stood on the remains of a pagan temple dedicated to Jupiter the Savior. Anyone who wonders what it looked like should be told that the church of the Santissimo Salvatore was a Romanesque church which had a nave and two side aisles, terminating in three apses. The façade was pierced by three portals, one in the center and one on each side. Over the centuries the church underwent various transformations, until the decision was made to tear it down and build a new one, designed by the Sienese architect Agostino Fantastici, in the first decade of the nineteenth century.
All that remains of the ancient Cathedral is the remnants of the main portal, visible in the first chapel of the left aisle, called the chapel of the Baptistery. The reliefs, carved out of travertine, present the iconography typical for main portals of churches: Jesus Christ the Redeemer imparting His blessing, two angels holding incense burners, and the symbols of the four evangelists: the lion (Saint Mark), the man with wings (Saint Matthew), the eagle (Saint John the Evangelist), and the ox (Saint Luke). Christ himself said: “I am the door; anyone who enters through me will be safe” (John 10:9). The act of crossing the threshold and entering the church brings us into the presence of Christ, Judge and Lord of history and of each person as his or her Savior. Through Him, Vanquisher of death and Lord of life, which is the meaning of the mandorla in which He is shown, man can reach the Glory of God. Knowledge of Christ is made possible by listening, through the Church, to His Word as handed down in the four Gospels. At the top of the composition is a cross, the instrument of death that became the tree of life by virtue of Christ’s sacrifice.