The whole city revolves around a place that is at once forbidden and indifferent, a residence masked by greenery, defended by moats, and inhabited by an Emperor who is never seen. First a feudal castle, Edo Castle became a palace in the 19C. It was destroyed during the war then reconstructed in 1968. You reach the palace via the exterior gardens with manicured lawns. A visit is interesting but frustrating as so few areas are open to the public.