The Church of San Pietro in Mezzana Casati, a hamlet of San Rocco al Porto, was probably built around 1573, as attested by a deed of the Piacenza notary Girolamo Cavalli. The church has a Latin cross plan with a single nave, two chapels located in the arms of the transept and a raised presbytery, all covered by cross vaults. Externally, the building has regular block masonry, a wooden roof covered with tiles and a square bell tower on the side. The interior decorations date back to different periods: in 1683 the fresco depicting St. John the Baptist was painted in the baptistery; in 1890 the painter Chizzoli from Lodi, commissioned by the parish priest Fr. Perotti, decorated the nave and the statue of St. Peter was purchased; in 1929 the Chapel of St. Paul was redecorated with stuccoes and canvases depicting the life of the Saint, while ten years later the painter Ugoni painted the vault.