Todoroki Keikoku is one of such places. Todoroki Keikoku, or Todoroki Valley as it could be called in English, is a great natural place in Tokyo where you can escape from the concrete and cramping that is prevalent in this mega-city. The Todoroki Keikuko is located in Setagaya-ku, and there is a nice article on getting to it by bus here.
The valley is about 1 km long and has a walking path along the shallow stream that runs along the length of the valley. It's fairly densely vegetated along the valley walls with shrubs and trees, so when you are in the valley you will get the feeling that you are completely away from Tokyo. It may not be the biggest of nature parks, but for Tokyo it is quite unique.
The water in Todoroki Keikoku
A family getting their photo taken by several people haha
At the opposite end of the Todoroki valley entrance there is a very nice shrine called Todoroki Fudo, where you can stop to pray or have a soft serve ice-cream hehe^^ There are also many small shrines dotted here and there along the valley which seem to blend in with the natural environment so well.
In addition to the shrines there are several small tombs that appear the date back to the 7th or 8th century. I didn't really notice any tombs, but if I had known I would have kept my eye out.
The Todoroki Keikoku is a really great place to relax or exercise. The trail is 1km, but there are lots of areas to explore and stairs to climb (to reach the Todoroki Fudo). Going back to the entrance is another 1km of course haha! However, make sure that you are wearing some shoes you don't care about much, because the trail is quite wet and muddy.
I didn't know better, so I wore shorts and thong sandals. By the time I got back to the entrance my legs were well splattered with mud and dirty water. I'm not naturey enough to enjoy that haha! I wish I could have spent more time enjoying the sights, rather than worrying about where I stepped!
A small shrine in Todoroki Keikoku
Now that summer is coming up, I think the Todoroki Keikoku is going to be a great place to visit. Cool air sinks, so the valley should be cooler than other areas and the trees block out sunlight. It must be a nice escape during the summer months in Japan, so perhaps I should check it out and see if my theory is correct XD
A little frog shrine
Banners over Todoroki Fudo
I only saw one other western tourist there, being guided by a Japanese friend. The rest of the tourists appeared to be Japanese. I hope that the Todoroki Keikoku gets more attention because it really is a lovely place to enjoy nature. But at the same time I don't want it to be spoiled haha.