The Concattedrale di San Siro stands at the edge of La Pigna's lower quarter and is one of the oldest religious buildings in Liguria. Its origins go back to late antiquity, though the current structure is largely medieval, remodelled in the Genoese Gothic style with the characteristic black-and-white striped stone interior that appears in churches throughout the region.
The cathedral's three naves are cool and dark, a pleasant refuge from the summer heat. Notable inside are a polyptych altarpiece attributed to the school of Luca Cambiaso, carved wooden choir stalls, and a marble font from the 16th century. The exterior is relatively plain, which makes the spacious interior all the more surprising. The piazza in front is a good place to sit and watch life in the lower old town.