Akan Mashu National Park

Listen first. On a still morning here, the loudest sound may be the steam. Somewhere nearby, the ground hisses and the air carries a faint smell of sulphur, like struck matches. Underfoot, the soil is warm in places where it has no reason to be. This is eastern Hokkaido, and the land beneath you is still very much alive.

Akan Mashu National Park is one of the oldest national parks in Japan. It was first protected in 1934, in the first group of parks the country ever created. For most of its life it was simply called Akan National Park. In 2017 its name changed to include Mashu, the lake that many visitors remember most. The park is not one single viewpoint. It is a wide landscape of volcanoes, forests, and three large lakes.

Those lakes sit inside calderas. A caldera is the giant bowl that forms when a volcano empties itself and the ground above collapses. Over thousands of years, rain and snowmelt filled these bowls with water. So when you look across a lake here, you are looking into the remains of an ancient eruption. The quiet surface hides a violent beginning, and the volcanoes around it are not finished yet.

Start with Lake Akan, in the west of the park. Its shores hold one of the strangest living things in Japan. They are called marimo — soft green balls of algae that roll slowly along the lake bed. Wave action and gentle currents turn them, again and again, so they grow into near-perfect spheres. Lake Akan is one of very few places on Earth where marimo grow this large. Japan protects them as a Special Natural Monument.

Here is something many visitors miss. Marimo are not plants inside a shell. They are made of fine algae threads, all growing outward from the centre. The round shape is a product of movement. Without the turning of the water, they would simply lie flat. Small souvenir marimo are sold in shops around the lake, but the large wild ones stay in the water, protected.

On the lakeshore sits Akan Kotan, a village of the Ainu. The Ainu are the indigenous people of Hokkaido. They lived on this island long before Japanese settlers arrived in large numbers. Akan Kotan is one of the largest Ainu communities in Hokkaido. Walk its main street and you will see workshops with carved wood, owls, bears, and patterns of curling lines. Many shops are run by Ainu families, and some carvers work in full view.

The Ainu and the marimo come together each autumn. Every October, Akan Kotan holds the Marimo Festival. It is a ceremony of thanks and protection for the algae balls of the lake. The festival grew from local concern in the twentieth century, when marimo were being taken from the lake in large numbers. Today it is a moment when Ainu songs, dances, and prayers are shared in public. If you are here in that season, it is worth asking about.

Not far from the village, follow the forest path to a place called Bokke. Here, small mud pools bubble and pop on the edge of the lake. The name comes from the Ainu language and refers to this boiling ground. The mud moves slowly, then breaks with a soft, wet sound. It is one of the clearest reminders that a volcano is working directly beneath your feet.

Now move east, to Lake Mashu. This lake has no large river flowing in and none flowing out. Its water comes mostly from rain and snow. Because so little enters from outside, the water has been famous for its clarity. On a clear day, the surface turns a deep, almost ink-like blue. Steep caldera walls drop straight into it, and visitors are not allowed down to the shore.

But Mashu is also famous for hiding. Fog often rolls in and fills the whole bowl like milk in a cup. Many people climb to the viewpoint and see only white. Locals have sayings about this. According to one popular tale, a visitor who sees the lake clearly on the first try will face some twist of fortune later in life. The details change depending on who tells it. Treat it as folklore — and a kind way to comfort anyone who arrives in the fog.

To the south of Mashu rises Mount Io, a low and steaming volcano. Its Japanese name means sulphur mountain. Vents in the rock push out hot gas with a steady roar. Around the vents, bright yellow sulphur crystals grow on the stones. The smell is strong, and the ground is pale and bare. For a long period, sulphur was mined here, and that industry helped bring roads and railways into this remote region.

Finally there is Lake Kussharo, the largest caldera lake in Japan. It feels open and gentle compared with Mashu. At Sunayu, on the eastern shore, hot water rises through the sand. Dig a little with your hands and the sand grows warm. In winter, whooper swans arrive from the north and gather where warm springs keep patches of water open. When the rest of the lake freezes, the ice sometimes cracks and pushes up into long ridges across the surface.

What ties all this together is heat and water, working side by side. Snow falls on volcanoes. Water fills craters. Hot springs feed the villages, and Kawayu Onsen, near Mount Io, has long welcomed bathers. The forests around the lakes hold deer, foxes, and birds. People have lived alongside this restless ground for centuries, and the Ainu gave names to much of it long before maps were printed.

So pause for a moment where you stand. Notice the temperature of the air. Notice whether you can smell sulphur, or only pine and cold water. Look at the colour of the lake, if you can see it, or the shape of the fog, if you cannot. As you walk on, listen again for that low hiss from the ground. It is the same sound that made this whole landscape.