Servicemembers looking for a relaxing day trip into the wilderness of western Tokyo can go straight to the water source for the metropolitan area and one of the largest dams in Japan.

Ogouchi Dam is a family-friendly destination about an hour’s drive from Yokota Air Base. Its reservoir holds 189 million tons of water for the people of Tokyo.

Construction began in 1938 to help serve the city’s rapidly increasing population. When it was finally completed in 1957 — the project was halted during World War II because of labor and material shortages and other problems — the 149-meter-high, 353-meter-long structure was billed as the largest dam in the world. Nearly 90 people died during its construction.

Beyond its entrance, Ogouchi stretches far back into Mount Mitake, a 929-meter summit that has been regarded as sacred since ancient times and is known for its Musashi Mitake Shinto shrine. The dam is shaped like a stretching coastline because it was designed to hold back the water along Mitake’s slopes.

At the bottom of the dam is the starting point for the Tama River, which flows through the Kanto Plain along the edge of the Musashino Plateau before reaching the sea near Haneda airport in Tokyo proper.

The dam’s observation tower also offers stunning views, and visitors can stroll across the structure and around the reservoir to various trailheads, including Mount Mitake’s Rock Garden route that takes hikers onto rocky trails past moss-covered stones, waterfalls and fresh mountain streams. The area is teeming with wildlife, including Japanese black bears.

There’s a large visitors center full of exhibitions about the dam, the importance of water and Okutama history.

The center also has a small cafeteria that serves Japanese staples like katsudon and miso soup. There are also a handful of eateries, including a small ramen shop, nearby.

onstott.allen@stripes.com

DIRECTIONS About an hour’s drive from Yokota Air Base in western Tokyo. By train, take the Ome line to Okutama Station, then take the Nishi Tokyo bus from the No. 2 bus stop and get off at Okutamako.

TIMES The dam’s visitors center is open 9:30 a.m. to 5 p.m. The building is closed Wednesdays (unless Wednesday is a holiday, then it is closed the following day) and during end-of-year and New Year’s holidays.

FOOD Food is served at the visitors center, and there are a handful of eateries, including a small ramen shop, near the dam.

INFORMATION 0428-86-2731; www.waterworks.metro.tokyo.jp/kouhou/pr/okutama (Japanese only)

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