In Nagano-Ken, there are many famous mountains above 2000m altitude. You can go there by JR-Chuo-line or JR-Hokuriku-Shinkansen. Yatsugatake : Chino-station
North Alps : Matsumoto, or Hotaka, Hakuba-station
Central Alps: Komagane-station
Please check nice photo in my blog as follows. You can see pretty and beautiful alpine plant.
長野県・常念岳
https://ameblo.jp/cx0293/entry-12435038468.html
If you prefer beach more than mountain, you can watch it below. You can take a kayak, and you may be able to watch many dolphin nearby a small boat.
東京都・小笠原諸島