Lake Mashu

Lake Mashu

Travel Guide

Lake Mashu

A mysterious lake, Lake Mashu is one of the world's clearest, most transparent and one of the deepest lakes in Japan. The lake is known for the mist and fog that often forms here, and as its name in the Ainu language, “Kamuy-tou”(Lake of the Gods), implies, it presents a stately and mysterious atmosphere.

The lake was catapulted to fame in the 1960s with the hit song, The Mists of Lake Mashu, and in 2001, was designated as a Hokkaido Heritage site.

Located in Akan National Park on the island of Hokkaido, Japan, Lake Mashu is a landlocked endorheic crater lake formed in the caldera of a potentially active volcano. With no incoming or outgoing river currents, the lake has a deeply serene, mirror-like surface.

There is a world ranking on lake water clarity in 1931, Lake Mashu attained a world record of 41.6 (136 ft) meters of visibility, exceeding that of Lake Baikal in Russia. Lake Baikal was measured around the same time measured 40.5 metres (133 ft). However, with the later introduction of sockeye salmon and rainbow trout into the lake, the transparency has shown a decreasing trend year after year. At the same time, a transparency survey has not been carried out on Lake Baikal in over 70 years, and with increasing development in the surrounding area, underwater visibility is thought to have significantly decreased. As the record is an old one, the truth is that no one really knows which lake is the world's clearest, but there is no doubt that Lake Mashu is at least one of the world's clearest, most transparent lakes.

The clarity of Lake Mashu’s water is not a mystery, but rather the result of miraculous divine intervention. Some time ago there was a special program on NHK about the mysteries behind the lake’s amazing underwater visibility. This program highlighted one of the divine interventions as the fact that it is not drained by any river. That is, the lack of inflowing water means no plankton or sediment is brought in that can impact clarity. The second divine intervention is that the lake’s primary source of water is rainfall and snowmelt, but its level remains the same throughout the seasons. Why is this? It’s because the lake features a unique all natural water filtration system of caldera lakes where the pressure at the lake’s depths pushes water through highly permeable volcanic rock that purifies the water, which eventually rises back to the surface. The third divine intervention was the lake was created in a place and topography that is not easily accessible by humankind. If just one of these elements was lacking, then the lake probably would not be able to boast the world’s foremost underwater visibility. This is why Lake Mashu can be called a miracle.

The tiny island of Kamyush lies at the center of Lake Mashu. This small spit of land is also known as the dimple of the lake, and its name in the Ainu language means, the old woman who became a god. This island rises as much as 30 meters from the lake surface, but in actuality it is part of the volcanic summit projecting its face from the water at an elevation of 240 meters.

Lake Mashu is distorted oval and is about 6km long and 3km across. It is lying 315 meters above sea level, surrounded by 300-400 meter high sheer cliffs, born from the fires of a massive volcanic eruption nearly 7,000 years ago, and dominated by Akan-dake, known as “The mountain of the Gods” to the Ainu people, at the lake’s south eastern edge. Slightly larger than Lake Akan, Lake Mashu has a circumference of 20kms, covers an area of 1,966 sqkm, and has a depth of 212 meters.

Lake Mashu was originally named Lake of the Devil by the Ainu. This was rendered as Lake Mashin by the Japanese. Over time, however, the Japanese began to refer to the lake by the Japanese reading for the neighboring peak, Mount Mashu-dake. The kanji for this peak translate roughly as scrubbed area mountain. The Ainu name for this peak, by which it is commonly known today, is Kamuinupuri or mountain of the gods. The lake also retains its Ainu name, Kamuito or lake of the gods.

Often enveloped in dense fog and mist, Lake Mashu has an image of being always covered in fog, and only sunny once in a blue moon. Because of this, it's said that those who see the lake when it's sunny and without fog will either not be able to marry until later in life, break up with a loved one if with that person at the time, or be unable to advance their career, and therefore jinxed.

They have a famous song called the Fog of Lake Mashu. Travelers who tend to bring sunny weather with them, fortunately or unfortunately, never get to see the fog of Lake Mashu. What do actual statistics say about this? According to data, fog at Lake Mashu peaks from June to July. During this time, the lake can be seen for an entire day only about 15 days a month, while the view is partially blocked about 10 days a month and completely blocked five to six days a month. There are many types of fog created based on the location, time and conditions, including ground fog rising from the surface of the lake and transient sea fog produced when the warm Kuroshio Current meets the cool Oyashio Current of the Pacific Ocean that travels all the way to Lake Mashu. However, don’t lament if you are not able to see Lake Mashu due to the fog. This is because you were able to witness the fog of Lake Mashu. Not only that, on the five or six days a month when the lake is totally covered in fog, the kamuy of Mt. Mashudake (Kamuy Nupuri, or mountain of the gods) may come down to the lake for a private swim away from prying eyes.

On the slopes around and above the lake grow a mixture of evergreen forest with Picea jezoensis and Abies sachalinensis and birch forest with Betula ermanii.

Visitors are not allowed to go down to the lake, however there are two observation decks positioned around the rim of the caldera from where you can enjoy views. Observation Deck Number 3 lies along the western rim of the caldera and consists of two decks with unobstructed views onto the lake and Mount Mashu-dake. Besides free parking, there are no facilities provided.

Heavy fog Ice fog Lake Mashu in the sunny day

Travel Advice


摩周湖神之子池- Kaminoko Pond is the pond which is about 7 to 8 km away from Mashu Observatory Deck. There is a parking lot 2 km from the Kaminoko Pond. Groundwater from Mashu Lake forms the clear-blue Kaminoko Pond. The pond is called Kaminoko (child of the gods) as the lake is formed by underflow water from Lake Mashu. Its aquamarine and emerald green waters are mysterious to behold and it’s no wonder it was given the name “Child of God Pond”. 12,000 tons of underflow water flows from the bottom of the lake every day. The pond is small with a circumference of 220 m and a depth of 5 m. Pond water is so clear that you can see the bottom of the pond. As the water temperature is low throughout the year at an average of 8 degree Celsius, fallen trees remain un-decomposed at the bottom of the pond. Red-spotted Dolly varden swimming through the fallen trees is a mysterious yet beautiful sight.

- Visitors might see beautiful fog ice between late December and mid January because of the foggy lake.

- Lake Mashu is located in Akan National Park, this means visitors are prohibited from approaching the lake's shoreline, and no homes or camps are allowed along the lake. Visitors are only allowed to enjoy the views of the lake from the Observation Deck.

Observation Deck No. 1

Located close to Mashu Hot Springs, Observation Deck No. 1 is the most popular of the three and easy offers a restaurant onsite. The view to the front includes Lake Mashu and its dimple Kamuishu Island as well as the jagged Mt. Kamui Nupuri (Mt. Mashudake), while you will find Mt. Shari rising in the distance. Don’t get caught up on the lake in front of you, as behind you is a panorama view overlooking the 500,000 hectare Konsen highlands, which is sure to impress any visitor to the area. Observation Deck Number 1 comes with a paid parking lot, multiple viewing decks, toilets and a large shopping area with a food stand offering various Hokkaido specialties.

Those who wish to view Lake Mashu from even more angles will enjoy the hiking trail, known as the Mashu-dake Hiking Course, which leads from Observation Deck Number 1 along the rim of the caldera a third around the lake to the summit of Mount Mashu-dake, the prominent volcanic peak on the western side of the lake. The trail leads through forest and grassland for about seven kilometers and takes about 2.5 to 3 hours to hike one way.

An Observation Deck No. 2 used to exist between decks number 1 and 3, but has been closed to the public.

Observation Deck No. 3

Observation Deck No. 3 is located about 4 km north of Observation Deck No. 1, and there is only a parking. Observation Deck No. 3 is situated close to Kawayu Hot Springs and affords up-close views of Kamuishu Island and in the distance the cliffs of Mt. Kamui Nupuri appear even steeper. Another attraction of this particular site is that it also affords panorama views of Lake Kussharo and Japan’s largest caldera, the Kussharo Caldera.

Uramashu Observation Deck

The Uramashu Observation Deck is located on the border of Kiyosato Town and Nakashibetsu Town. It’s called “Uramashu” (literally “the back of Mashu”) because it is situated on the direct opposite side of the lake from Observation Deck No. 1. This side of the lake sees relatively less fog and offers a better chance of seeing the lake surface. In this sense, it is considered somewhat of a secret viewing spot for Lake Mashu.

- Chinchilla is living around the lake and visitors might happen the see them. Some shop at the observation deck sells the food for chinchilla.

- The Fog Can is a specialty of Lake Mashu, although there is nothing inside. But the Can is a good souvenirs, visitors can write message on the can, and can also be mailed. In addition, Lake Mashu pattern will emerge by wrap the Can with hand.

- Sometimes the visibility is only a meter because of the fog. But visitors don’t be discouraged, because even the Japanese travelers can barely have the clear view of Lake Mashu.

- The ice cream of Ice of Lake Mashu is recommended. Please find the yellow colored store at the corner of national highway 243 and Hokkaido highway. Please see the Japanese official site of Ice of Lake Mashu for access map.

The legend of Lake Mashu

There was a conflict between two Groups: Ainu people at night of Bear Festival. People of the defeated group was almost be killed. Only an elder woman and her grandson escaped but the child was lost. The elder woman reached unknowingly the Lake Mashu while searching the boy and decided to stay there overnight. The elder woman was worried about the boy but she could walk anymore. Day after day, the elder woman turned into Kamuishu Island. Now, when anyone approaches the Lake Mashu, the elder woman cries for finding the boy and the tiers is rain, snow and fog.



Address Teshikaga-cho, Kawakami-gun, Hokkaido
Phone 015-482-2200(Lake Mashu Tourist Assosiation)
Admission Free  
Hours Free time  
Closed Open 7 Days a Week
Duration 15 minutes
Getting There By Train
25 minutes ride by Akan Bus from JR Mashu Station to the final bus stop, then walk approximately 1 minute.

By Car
Take Doto Expressway to the Ashoro exit and take National Highway route 241, 243 and Hokkido Highway route 52. It is approximately 120 kilometers 2 hours from exit.
Observation Deck No. 1 Paid parking available
Observation Deck No. 3 Free parking available
Uramashu Observation Deck Free parking available

Attractions in Japan