Ogouchi Reservoir 小河内貯水池（奥多摩湖）

Visit one of Japan's biggest reservoirs

As one of the largest drinking water reservoirs in Japan, Ogouchi Reservoir holds about 185 million tons of water to supply the people of Tokyo. The 149-meter-high and 353-meter-long dam took 19 years to complete.

You can get a good look at the impressive dam from the observation deck, which also offers a great view of the area. There's a 12 km "Lake Okutama Ikoi Road" from the dam to the Furusato Mountain Village (Yama no furusato mura). It's a nice long walk which lets you take in the lakeside scenery. The path is closed in the winter, so make sure to check if it's open before going.

*Lake Okutama Ikoi Road may be closed due to inclement weather conditions, during winter or due to construction. Please see the Tokyo Metropolitan Government Bureau of Waterworks website for details.