Koishikawa Korakuen Garden, completed by Tokugawa Mitsukuni (known as "Lord Mito"), is an urban oasis located right next to the Tokyo Dome, as shown in the photo below, yet boasting a total area of ??over 70,000 square meters.

As you can see from the map above, there are large and small ponds connected by streams, suggesting a well-established ecosystem. I went there hoping to find the Japanese pond turtle, a species endemic to Japan. 　(Nihedon @ KesaranPasaran Lab)