Girona has plenty of religious buildings that are worth checking out, perhaps not necessarily because of the subject, but more because of the architecture. One such building is the Església de Sant Feliu, or the Church of Saint Felix.
It's a very old church, with Gothic and Romanesque influences. It was constructed from the 12th to the 17th centuries, and has been the office of the Parish of Sant Feliu, or the Roman Catholic diocese in Girona. This church predates the cathedral.
There are some notable Roman and early Christian sarcophagi dating from the 3rd and 4th centuries, and there's also the notable tomb of Narcissus of Girona, who according to history is one of the first bishops of the area.