In the territory of this comune there are seven castles, and the first is the one that gives it its name: in 948 Lothair II of Italy authorised the canons of Piacenza cathedral to build fortifications in defence of the parish church of San Giorgio, after the Hungarian raids, and the work began. That castle was destroyed twice, the second time in 1242 by the militias of Bergamo and Cremona under the command of the marquis Lancia; then it passed to the Anguissola and in the sixteen hundreds to the Scotti, and today it is the seat of the comune. The other six are Montanaro, Ronco, Rizzolo, Tollara, Viustino and the Rocca. But the one worth telling about is Tollara, and for an upside-down reason: in the chronicles of the fighting that took place in this area it is almost never mentioned, which according to scholars testifies to the fortress's substantial extraneousness to those events. In a valley full of castles destroyed and rebuilt, there is one that stands out because nothing ever happened to it; today it has been turned over to farm use.
The Rocca was built in 1604, perhaps to a design by Vignola, and called the new fortress to tell it from the old castle; in the eighteen hundreds it was frescoed by Giuseppe Badiaschi of Piacenza, and its park of seventy-five thousand square metres has a lake, a neo-Doric temple and a system of grottoes unique in the Piacenza country, which was not in the original design and which the Milanese Ambrogio Rossi added in 1840. The castle of Montanaro, on the other hand, has had three lives in two hundred years: in 1799 it housed the Austro-Russian troops of general Suvorov, under fascism it was the seat of the GIL youth organisation, and in the end it became the provincial foundling hospital. In 1862, after the unification of Italy, the comune added the specification «Piacentino» to its name. And there is a last, recent chapter: since 1961 the hamlet of San Damiano has been internationally known for the Marian apparitions reported by the peasant woman Rosa Quattrini, who said she saw the Virgin every Friday at noon, and who in 1967 reported her calling the water of San Damiano «the holiest in the world». Those apparitions are not recognised as authentic by the Catholic Church, and no examination of any kind is under way with a view to a possible recognition.