Four or five years ago, standing alone in front of the clear, gently bubbling waters of Kiyomasa no Ido, a natural spring secreted in woodland at the far end of the Meiji Shrine's iris garden, I strained to detect any sound, but even the noise from car horns was smothered and muted by the grove. If I had to elect the single-most tranquil spot in Tokyo, this would have been it.