You'll probably spot Cathedral of Cittadella from a distance before you actually find this important religious building. Look around inside if the doors are open or just admire the facade from outside.
This principal church is often on the itineraries of travelers to Cittadella. But Cathedral of Cittadella isn't the only drawcard here. Parco dell'Amicizia, Porte Padova, and Porte Bassanesi are some other worthwhile attractions close by.