Running through Akiruno City (あきる野市) in the foothills of Okutama, to the west of Tokyo, the Akigawa River (秋川) and its valley can give you all you need for a quick outdoors escape from the bustle of the city. Dramatic scenery, deep pools and a BBQ spot. If you’re on a limited timeframe you could do a lot worse than come out here for some fresh air and water. .
Musashi-Itsukaichi (武蔵五日市) is the go-to jump off point, and though technically a part of 東京都 (Tokyo Metropolis) you won’t find much in the way of facilities on hand, more a quiet, roadside wooden village feeling. The river round here is deep in parts and has some solid rock jumping potential, summertime tubing down the river, and nice pebble banks for picnics.
If you diverge from the river there’s some impressive farmland surrounding: think classic landscaped paddy fields stepping up little hills, with some pleasant Temples and Shrines. see the Gotokuji Temple (広徳寺) and Mishima Shrine (三島神社) for some fine examples.
To top it all, you can warm up after a day in the river with a coniferous tree-top, birds-nest onsen with impressive outdoor baths.