You needn't have a strong religious faith to appreciate the peaceful atmosphere of Duomo. Check when the next service starts or when it's open for general viewing.
This principal church is often on the itineraries of travelers to Cremona. But Santa Maria Assunta Cathedral isn't the only drawcard in the area. Cathedral of Cremona, Museo del Violino of Cremona, and Torrazzo of Cremona are some other worthwhile attractions close by.