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Kushiro, Hokkaido
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Akan-Mashū is built around three great volcanic calderas: Akan, Kussharo and Mashū, each with its own lakes and volcanic landscapes.
Lake Akan is the world's only known habitat where marimo form today's extensive colonies of giant, beautifully spherical balls.
Some Lake Akan marimo grow beyond 30 cm across, and the lake has been estimated to contain hundreds of millions of spherical aggregations.
Himemasu, a landlocked form of sockeye salmon native to Lake Akan, is a prized local food eaten grilled and, when exceptionally fresh, as sashimi.
In winter, people fish for wakasagi through Lake Akan's ice and can eat their freshly caught fish as tempura.
Akan-Mashū was designated in 1934, making it one of Japan's earliest National Parks.
Until 2017 it was called Akan National Park. Adding “Mashū” recognized the importance of the park's eastern landscape.
Lake Kussharo is Japan's largest caldera lake, covering about 80 square kilometers.
Lake Mashū recorded an extraordinary 41.6 m transparency in 1931, then a world record.
Lake Mashū has no rivers flowing into or out of it, helping keep nutrient and suspended-particle levels exceptionally low.
The intense blue created by Mashū's clear water is known as Mashū Blue.
Mashū is also famous for fog, earning the nickname “Foggy Lake Mashū.”
Atosanupuri means bare mountain in the Ainu language, describing the steaming volcanic slopes visitors can see today.
Atosanupuri has more than 1,500 vents, with steam still escaping continuously from the volcanic ground.
Around Atosanupuri, volcanic gases and acidic soil allow alpine plants to grow at only about 150 meters elevation.
Roughly 100 hectares of Ezoh-isotsutsuji bloom white near Atosanupuri in June and early July.
Kawayu Onsen's hot water originates beneath Atosanupuri, and a literal “river of hot water” runs through the town.
Onnetō is an Ainu-derived lake name, and its changing water colors have earned it the nickname Five-Colored Lake.
Onnetō Yunotaki is a rare place where microorganisms help create manganese oxide from mineral-rich hot-spring water.
Manganese deposits at Onnetō Yunotaki were once mined, with roughly 3,500 tons extracted in the mid-20th century.
Meakan-dake rises to 1,499 m and remains an active volcano with steaming craters visible near its summit.
Meakan-dake gives its name to alpine plants including Meakan-kinbai and Meakan-fusuma.
Geothermal heat keeps parts of the Wakoto Peninsula unusually warm, allowing some organisms to survive surprisingly far north.
When Lake Kussharo freezes, moving ice can form long ridges called omiwatari, a phenomenon whose Japanese name evokes a deity crossing the lake.
Hot springs keep parts of Lake Kussharo ice-free in winter, attracting hundreds of whooper swans from Siberia.
At Sunayu on Lake Kussharo, digging into the lakeshore sand can expose naturally heated geothermal water.
Penketo and Panketo mean “upper lake” and “lower lake” in Ainu, describing their actual positions in the watershed.
Penketo and Panketo are so strictly protected that ordinary public access is generally prohibited.
Akan Ainu Kotan is one of Hokkaido's largest Ainu communities, where woodcarving, embroidery, dance and cultural expression remain active.
At Akan Ainu Kotan, artisans keep woodcarving and embroidery traditions alive while creating new work inspired by inherited Ainu designs.
Lake Akan's Marimo Festival began in 1950 and combines conservation with Ainu prayers and the ceremonial return of marimo to the lake.
Kaminoko-ike, “Child of God Pond,” takes its name from a tradition connecting its brilliantly clear spring water with sacred Lake Mashū.
