Once eyes have adjusted to the interior from the bright sunshine of the square it can be seen that the cathedral is laid out in the traditional pattern of the Romanesque Latin cross along with two side aisles flanking the central nave. This original layout is still clearly visible despite the cathedral being totally modified under the auspices of Bishop Serguidi in the late XVI century. This remodeling enthusiastically followed reforms laid down by the Council of Trent, a counter-reformation movement aimed at strengthening the Catholic church against the growing popularity of Protestantism in Europe. During the remodeling, the columns that divide the nave from the aisles were richly decorated in stucco worked by Gianpaolo Rossetti with their capitals embellished by Leonardo Ricciarelli. A sculptured frieze in Montecatini stone was left in place from an earlier period to provide a framework for the cathedral's six main altars. During this period graciously arched Romanesque windows were replaced by more severe rectangular windows befitting a serious reformation.