The Narnia exhibit is located in a stage set building near the Backlot Studio Tour side of the park. It is a museum like setup with different props, costumes and sets from Disney movies. The exhibits located in this building rotate depending on what Disney movies have recently come out. At various times I have seen items from 101 Dalmatians, Haunted Mansion movie, and this year Narnia.
In the rumor mill, the next exhibit is reportedly POTC which makes sense as Disney's biggest money maker.
PS at the end of the Backlot Studio Tour, you can see Barbossa's costume. Very cool!!