Otatomari Swamp, located in the southeast of the island, is about 1 km in circumference and is the largest lake on Rishiri Island. There is a partially unpaved promenade around the swamp, so visitors can take a walk while enjoying the reflection of Mount Rishiri on the lake surface. Around the swamp is the largest marshland on Rishiri Island, Numaura Marsh (designated as a natural monument by Rishirifuji Town), and Mikazukinuma Swamp. In the parking lot, there are the Rishirifuji Rest House ("Matchan's Restaurant", "Strait Sushi Nobuchan", and "Wakasan's Restaurant") and Rishiri Kameichi Otatomari-numa Restaurant, where you can buy local specialties and souvenirs and taste "scallop pancake", "sea urchin gunkanmaki", "Kumazasa soft", "Manyenyuki soft", etc.