The ancient Temple of Minerva was converted into a Christian Church (San Donato) in the Middle Ages. In 1212, the Abbot of San Benedetto Maccabeo granted an extended lease to the consuls of City Hall “il casalino di San Donato”, in other words a cell in the temple, continuing the use of the rooms between the columns. This cell became the residence of the Chief Magistrate, except for the lower part, which served as a jail.

One Giotto’s frescoes in the upper part of Saint Francis’ Basilica recalls its original destinantion as jail with grates on the windows. In 1228 the City purchased some houses across from the temple with the purpose of enlarging the square. At the same time, the vestibule between the columns was released and became the seat of the Arengo. Only in 1456 did the building return to its original religious purpose and became dedicated to the Madonna (1539), with the name of Santa Maria Sopra Minerva.