4088-4088 Travel Guide

The Lake Akan Summer Observatory (Akan Lakeside Observatory) sits inside the national Akan Lakeside Ski Area on Mount Shira-yu, at about 530 metres in Kushiro's Akan-cho, and is free. A ramp opens onto sweeping views of Lake Akan, Mount Oakan and the Akan caldera; it runs from mid-May to October and closes in winter.

The Marimo Exhibition and Observation Center is not on the lakeshore at Akanko Onsen but on Churui Island in the middle of Lake Akan, and that single fact shapes the visit: it can only be reached on the Akan sightseeing cruise, has no separate ticket office and no road access. The boat circles the lake in 85 to 90 minutes and stops at the island, with the centre included in the fare. The highlight inside is a large tank reproducing the lake bed, where real marimo of different sizes and growth stages are displayed alongside microscopes, models and interactive panels explaining how these green spheres roll in clear cold water and slowly grow over decades. Lake Akan's marimo can reach 20 to 30 centimetres across, were designated a Special Natural Monument in 1952, and may not be taken from the lake; the souvenir balls in the hot-spring town are cultivated. Boats normally run from late April to November and stop when the lake freezes, with first and last sailings changing by month. Time on the island is often only fifteen to twenty minutes, so be in the first group ashore if you want a careful look. From 8 to 10 October each year the local Ainu community holds the Marimo Festival, returning the algae to the lake in a torchlit ceremony of thanks, the best moment to understand why marimo are more than a souvenir. Plan a half day combining the hot-spring town, the Ainu kotan, the cruise and the centre rather than hunting for a building on the shore that does not exist.

At 1,499 metres, Meakan-dake is the active volcano of Akan-Mashu National Park and, with Oakan-dake and Akan-Fuji, part of the Akan volcanic group; Fukada Kyukaya made it one of the Hundred Famous Mountains of Japan. Its upper slopes are bare tephra and sulphur fumaroles, its middle slopes carry endemic alpine plants such as meakan-kimme and meakan-fusuma, and on a clear day the summit looks over Lake Akan, Onneto and the distant Shiretoko range. June's alpine flowers and October's foliage are the two finest windows. The restriction, however, has to come first: on 15 September 2025 the Japan Meteorological Agency raised the alert to level 2, closing a 500-metre zone around Pon-Machineshiri crater, cutting the Lake Akan route above the sixth station and both the Meakan Onsen and Onneto routes above the seventh. Volcanic earthquakes spiked to 127 in a single day in May 2026, and as of autumn 2026 all three trails still cannot reach the summit. This is not a mountain you can climb after a weather check, and any itinerary promising a walk to the fuming crater is out of date. What still works: the Takiguchi trailhead for Oakan-dake lies outside the zone and makes a six-hour return hike; the road and lakeside path at Onneto are open, with water that shifts through five colours and the best view of the volcano's eastern flank; and Akanko Onsen and Meakan Onsen operate as usual. Brown bears are seen often here, so carry a bell even for the lakeside stroll, and follow current JMA volcano information or ask Kushiro City rather than an old guidebook.

Lake Mashū in Teshikaga, Hokkaidō, Japan, lies within Akan-Mashū National Park, a caldera lake formed when a volcano collapsed roughly seven thousand years ago. It covers about 19.6 sq km, plunges to 211.4 m and sits 351 m above sea level, ringed by cliffs more than three hundred metres high. No river flows in or out — the lake is fed only by rain and snow — and with almost nothing washed in from outside, a transparency of 41.6 m was recorded in 1931, the clearest in the world at the time; on bright days the water shows the near-ink blue known as 'Mashū blue'. Thick fog so often fills the basin that it is called the lake of mist, and locals treat a clear view as good fortune. Kamuishu Island at its centre and Mt Mashū (Kamuinupuri) to the east are both dwellings of spirits in Ainu tradition. To protect the water, swimming and fishing on the shore are prohibited, so visits mean looking down from the First and Third Lookouts, superb amid autumn colour or winter frost.