Institute for Nature Study, Meguro

For anyone in Tokyo interested in parks or other oases of nature in this metropolitan infinity, I would highly recommend the Institute for Nature Study. This nature reserve is five minutes' walk from Meguro station and right next to the Tokyo expressway, but to enter is like crossing a gateway between dimensions.

From the profusion of plants, bird calls, pond and insect life, and peaceful spiders on massive webs, it is quickly apparent that this must be one of the most biodiverse grounds in Tokyo. It is small enough to walk all the way around in one or two hours, but still lets you experience the sense that you've left the city far behind.

Well worth exploring. And if animals particulary interest you, go here and here too. I can assure you you will not be disappointed.