Located at the place at a height of 1,400m in the Nikko National Park, Senjogahara is one of the largest high moor in Honshu (main island of Japan). It is said that the lake formed by an eruption of Mt. Nantaisan turned to the more than 400ha marsh over time. This huge area encompasses more than 350 species of native plants and various types of wild birds, and 175ha out of the gross area is registered under the Ramsar Convention as “Oku-Nikko-shitsugen” (the marsh in Oku-Nikko). The most recommendable period to visit this area is the middle of June to the beginning of August when Cotton-Sedges and Meadow Sweets are in full bloom, as well as the end of September to the beginning of October when grasses to turn to red.