Jinpukaku is a graceful white villa at the foot of the castle hill, built in the Meiji period when Western styles were being folded into Japanese elite architecture. Its balconies, columns, and spiral staircase make it stand out sharply from the surrounding temples and stone walls.
It is an easy add-on to the castle ruins. Go for the architecture and for the way it shows Tottori shifting from feudal seat to modern prefectural capital.