Museu d'Art occupies the former Episcopal Palace beside Girona Cathedral, which already gives it a better setting than many provincial museums. Inside, the collection is strongest on Romanesque and Gothic art from the Girona region, with altarpieces, sculpture, and church objects that help explain the city around you.
This is a good museum to visit after walking the old quarter rather than before. The stone lanes, cathedral steps, and surviving medieval walls make more sense when you have seen the religious art and patronage that shaped them.