My wife and a friend have told me a few times to check out Todoroki Ravine Park here in Tokyo. It took me about 20 minutes to get there from my house and, more than once, I asked myself why I haven't been there before. It's so close to where I live, and people who are visiting Tokyo need to see this place.
I shot a quick video about it: https://youtu.be/qvCunT0IcUc
Descriptions of where it's located can be found in the video's description. I hope you can make it to this wonderful getaway.