 Under Gian Galeazzo Visconti the territory of San Genesio was included in the vast Visconti Park, extending between the castle of Pavia and the Certosa and included in a wall delimiting its perimeter.The wall was interrupted at certain locations by gates (porte) from which are derived the names of Porta Pescarina and Due Porte, two of hamlets included in San Genesio ed Uniti territory.following the fall of the Sforza the park was neglected and decayed, although its area was still identified as administrative district (Parco Nuovo).