The Iwate Museum of Art is Morioka's strongest modern indoor sight, a clean-lined gallery southwest of the centre with a permanent collection focused on artists connected to the prefecture. It is a good counterweight to the castle and temples: quieter, more spacious, and less tied to the usual feudal-city story.
Temporary exhibitions are often the main reason to go, so check the schedule before crossing town. Even without a major show, the building and collection make it worth the short bus or taxi ride.