Senjogahara Marshland

The Senjogahara Marshland (戦場ヶ原, Senjōgahara) is an expansive area of four square kilometers located north of Lake Chuzenji. Situated at an elevation of 1,400 meters above sea level, this highland plateau is one of Nikko’s most celebrated natural landmarks. The name “Senjogahara” literally translates to “Battlefield,” a reference to a mythical conflict between the mountain gods of Mount Nantai and Mount Akagi over the possession of Lake Chuzenji. Today, the area is a tranquil sanctuary, famous for the raised wooden boardwalks that allow visitors to traverse the delicate ecosystem without disturbing the ground.

Geologically, the marshland was formed when the Daiya River was dammed by a lava flow from Mount Nantai, creating a lake that gradually silted up over thousands of years into a peat-rich wetland. It is now recognized as a Ramsar site, a wetland of international importance, providing a vital habitat for over 350 species of plants and a diverse population of migratory birds. The scenery shifts dramatically with the seasons; in early summer, the marshes are dotted with the white blooms of cotton grass, while the summer months bring a lush green carpet of alpine flora.

The hiking trails are particularly popular during the autumn months. In late September, the marsh grasses turn a shimmering golden-brown—a phenomenon known locally as “grass autumn”—which precedes the vibrant red and yellow foliage of the surrounding larch and maple trees in October. The effortless, flat terrain makes the route ideal for birdwatching or long-distance trekking toward the neighboring waterfalls. With the volcanic peak of Mount Nantai looming in the background, the marshland offers one of the most vast and unobstructed natural vistas in all of Nikko National Park.