Each cardinal takes on a titular church, either a church in the city of Rome or one of the suburbicarian sees. The only exception is for patriarchs of Eastern Catholic Churches. Nevertheless, cardinals possess no power of governance nor are they to intervene in any way in matters which pertain to the administration of goods, discipline, or the service of their titular churches. They are allowed to celebrate Mass and hear confessions and lead visits and pilgrimages to their titular churches, in coordination with the staff of the church. They often support their churches monetarily, and many Cardinals do keep in contact with the pastoral staffs of their titular churches.
Where do the cardinals work?
a church in the city of Rome or one of the suburbicarian sees