The pantheon gives a very special touch in the mornings or at night through the shutters while you have your coffee/tea/whatever. The space is very cozy with lots of things to check out nearby: shops, groceries, art, tourist attraction, etc. I walked around often and found the walks to be very scenic and lovely.
However, it can get very noisy at night from the street, depending on the time you go, and the walls are thin so keep this in mind and/or pack some earplugs.