At an altitude of 1400 meters above sea level, the Senjogahara Marshland (戦場ヶ原, Senjōgahara) covers the plateau between Lake Chuzenji and Yumoto Onsen. It offers some of the best hiking in the Nikko National Park and is particularly beautiful during the autumn leaf season in October when the marshland's grasses turn into a reddish yellow and the larch trees into a shiny gold.
The Senjogahara Plateau Nature Trail follows Yukawa River during most of its course between Yumoto Onsen and Ryuzu Waterfall near the shores of Lake Chuzenji. The hiking trail offers excellent views of the marshland and surrounding mountains, and it takes around 2.5 to 3 hours to complete. Not far from Senjogahara lies Odashirogahara, a smaller but equally idyllic marshland, which is worth a detour or separate visit.
During winter, the marshland is usually covered by several centimeters of snow typically between December and March, during which the hiking trails may not be passable. But when enough snow accumulates, visitors can see a different side of the marshland by walking along the hiking trails on snowshoes. There is also a course network for cross-country skiing north of the Sanbonmatsu parking lot.
A couple of rest houses at the Sanbonmatsu parking lot offer snowshoe rentals for around 500 yen for two hours or 1000 yen per day. Cross-country ski rentals go for 1800 to 2000 yen per day. There are also guided half-day tours available, but advance reservations are required, and English instructions may be limited.
Senjogahara is connected with central Nikko by Tobu bus. Buses leave from Tobu Nikko Station (many also serve JR Nikko Station) and are bound for Yumoto Onsen. There are one or two buses per hour. The one way trip from Tobu Nikko Station to Senjogahara takes about 70 minutes, costs around 1500 yen and is covered by the Nikko All Area Pass.
A 2-day pass for unlimited bus rides between Nikko and Senjogahara (as far as Sanbonmatsu bus stop) is available for 2650 yen at Tobu Nikko Station, while a 2-day pass for unlimited bus rides between Nikko and Yumoto Onsen is available for 3000 yen.
For walking the entire Senjogahara Plateau Nature Trail, get off at either Yumoto Onsen or Ryuzu no taki bus stop. The hiking trails can also be joined from Akanuma bus stop, while Sanbonmatsu bus stop offers a small observation deck with views over the marshland, but no access to the hiking trails.
A separate bus travels between the parking lot near the Akanuma Shako bus stop at the southeastern end of Senjogahara Marshland and Senjugahama bus stop at the western bank of Lake Chuzenji, stopping at Odashirogahara Marshland and Lake Sainoko along the way. The entire one way trip takes approximately 30 minutes and costs 300 yen. Buses operate from late April through November about once per hour. More frequently on weekends and during busy seasons. These buses are also covered by the Nikko All Area Pass.
Note that during the autumn leaf season in October, traffic between central Nikko and Senjogahara can be very heavy, and buses can incur heavy delays, especially on weekends. If possible, try to visit during the week and not on weekends.