Na'in's Valiye Asr Zurkhaneh is the most accessible of the town's traditional houses of strength. Visitors can sometimes watch a session of zurkhaneh, the old Iranian athletic tradition that combines ritual movement, music, strength training, and ideas of chivalry.
Ask locally before going, as sessions are not run like fixed museum hours. It is most interesting if you have already seen Na'in's older mosques and houses and want a living cultural stop rather than another monument.