Things to do outside Tokyo

Hi.I'll be visiting Japan around early April and I am wondering if there is anything I can do outside of Tokyo, perhaps? I'm looking more into nature and less noise and hassle such as in Tokyo.I'm not very keen on Hakone and Lake Kawaguchiko either because I've visited those places before. I look forward to hearing from anyone. Feel free to answer!

There are many onsen and mountains north of Tokyo:
http://www.japan-guide.com/list/e1209.html
http://www.japan-guide.com/list/e1210.html

And more nature and monkeys in nearby Nagano:
http://www.japan-guide.com/list/e1216.html

Beyond what Uji posted, close to Tokyo is also Enoshima and Kamakura, which are very nice. You could also go to Yamanashi as well. Even within Tokyo, visiting one of the many gardens gets away from that "crowded city" feel and can refresh you without traveling too far!

Thanks Uji and Scarreddragon. I've been to Karuizawa and its really interesting there. Are any of the cities above sort of like karuizawa . I'm looking more into a daytrip activity sort of thing.

Also, is the Kanto area pass valid all the way to Nagano or just Karuizawa?

Thanks.

My vote would go to Mount Takao, if you need to escape city life.