Hokkaido Official Tourism Site HOKKAIDO LOVE!

A caldera lake formed by a volcanic eruption about 150,000 years ago. Four islands — Oshima, Kojima, Yaitai Island, and Churui Island — are scattered across the lake.

Surrounded by Mt. Meakan and Mt. Oakan, this nature-rich lake has hot springs flowing along its southern shore at Akan Onsen. Lake Akan is home to a unique ecosystem, and its most iconic feature is the "Marimo of Lake Akan," designated as a Special Natural Monument. Marimo is a type of freshwater green algae characterized by its perfectly round, spherical shape. You can see them at the Marimo Exhibition and Observation Center on Churui Island, accessible by sightseeing boat, or at the Akanko Visitor Center in the hot spring town. The scenery of each season is another attraction of Lake Akan. In summer, activities such as canoeing and trekking let you fully enjoy the great outdoors. During the "Lake Akan Marimo Festival" held every year from 10/8 to 10/10, the "Torch Procession" illuminates the hot spring town with flames of prayer, creating a magical atmosphere. In winter, on cold mornings, you may witness the spectacular sight of "Frost Flowers" — frost crystals that bloom across the frozen lake surface. On the thick ice, you can enjoy smelt fishing and snowmobiling. "Toukabi," a popular event where fireworks are launched over the frozen lake, is held every year from February to March.