It's quite possible to escape the madness of Tokyo in its many parks and japanese gardens, and Koishikawa Korakuen is living proof that these act as lungs within a megalopolis that seems to never end. Quite central inside the capital, Koishikawa is located north of the imperial gardens, just adjacent to Tokyo Dome, the huge stadium / concert hall.
During the visit, you'll walk along small trails around the main pond, but rarely Tokyo Dome City and other neighboring buildings will be forgotten in the background. Yet Koishikawa Korakuen dates back in the XVIIth century, at the beginning of the Edo era, making it one of the oldest Japanese gardens in Tokyo.
I had the opportunity to visit it during late November, the season of momiji (red maple trees).
Note that there is another Korakuen located in Okayama, near Shikoku island.