If you're jetlagged or working late but you still want to get in a workout, the branch of Gold's Gym in Harajuku is open 24 hours a day* and offers a one-day pass for non-members. There's a good range of weight-training and cardio equipment, including exercise bikes with a panoramic view, but no swimming pool. [*The gym is closed from 8pm Sundays until 7am Mondays, and on the third Monday of each month.]