 The comune of San Siro incorporates the "frazioni" (municipal fractions) of Acquaseria, Camnasco, Carcente, Gallio, La Torre, Lancio Lucena, Marena, Mastena, Maso, Molvedo, Noledo, Pezzo, Rezzonico, Roncate, Santa Maria, San Martino, Soriano and Trecciano.San Siro borders the following municipalities