The small building, from which derives the name of the densely-populated area that now includes it, was built at the end of XVII century for an initiative of a member of the Casoni family, whose coat of arms recurs many times in the inside.

In 1699 not only the building but also its decorations are completed. Bishop Naselli, in visiting it, said that the dome and the walls are decorated with fine paintings (pulchris picturis) and precious marbles.
The beginning of the construction is about, with all probability, around 1686 when the Senate of Genoa approved the institution of a solemn procession on the Trinity day: this oratory, therefore, represented the end of the procession.

A study of the building reveals two different building phases, old, one after another and this idea is confirmed also by the decoration of the dome, as, under the plaster on which are painted some pictures, there is a layer with simple decorations without figures. The picture of the dome shows the Trinity in the act of crowning the Vergin in front of Our Ancestors and other saints; the author of this painting should be recognized by his style as Stefano Lemmi from Fivizzano, who worked a lot not only in Sarzana but also in other places of Lunigiana.

Text of Pietro Donati