The Site is located in the northern part of the Tochigi Prefecture and includes Senjogahara mire, Odashirogahara mire and Lake Yunoko, which were formed from volcanic activities of Mount Nantai and Mount Mitsudake. The mires feature permanent forested peatlands, which are rare to this biogeographical region and are protected within the Nikko National Park. Over 100 plant species are found in the Senjogahara area, some of them genetically distinct in the region. The high prevalence of sika deer (Cervus nippon) has had a negative impact on the native flowers and butterflies in this area, so their numbers have been controlled and a fence has been constructed to protect the native plants. The Odashirogahara area also features some grasslands and woodland, which are declining due to urbanization and agricultural expansion. The grasslands of Odashirogahara and Lake Yunoko provide essential foraging and breeding grounds for various migratory waterbirds such as Eurasian wigeon (Anas penelope) and tundra swan (Cygnus columbianus). The Site has a management and restoration plan.