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Emerald-green Okama crater lake ringed by grey volcanic walls on Mount Zao
Photo: Qwert1234, Public domain, via Wikimedia Commons
Yamagata · lake

Okama Crater (Zao)

蔵王の御釜

A crater lake near the summit of the Zao mountains on the Yamagata-Miyagi border, its emerald water changing colour with the light. Open spring to autumn only.

Okama crater lake on Mount Zao with striped volcanic slopes around the green water
Photo: f_a_r_e_w_e_l_l, CC BY-SA 2.0, via Wikimedia Commons
Turquoise Okama lake in its crater with autumn-coloured slopes of Mount Zao
Photo: Fumihiko Ueno, CC BY 3.0, via Wikimedia Commons

A crater lake ringed by three peaks

Okama is a crater lake in the Zao mountain range, which straddles the border between Yamagata and Miyagi prefectures. Surrounded by three peaks, Mount Katta, Mount Kumano and Mount Goshiki, it is regarded as a symbol of Zao alongside the famous juhyo (the "snow monsters", trees encased in frost and snow). The lake itself lies on the Miyagi side, but you can reach the viewing platform from either Yamagata or Miyagi.

Its name comes from its shape, which resembles a kama (a round pot for cooking rice). Measurements taken in 1968 put its maximum depth at 27.6 m and its circumference at about 1,080 m.

Water that changes colour

The water of Okama looks emerald green, but depending on the strength of the sunlight and the angle you see it from, it shifts to deep green, blue and other shades. That is why it is also called Goshikinuma, the "five-coloured pond".

The lake water is strongly acidic, and nothing can live in it. Mount Zao is still an active volcano, and the Japan Meteorological Agency keeps it under continuous observation.

When you can go and how to get there

The Zao Echo Line, the mountain road leading towards Okama, and the Zao High Line, the 2.5 km toll road that branches off it, are closed in winter because of snow and are normally open only from late April to early November. During parts of spring and autumn they are also closed at night.

At the end of the High Line is the prefecture-run Zao Summit Rest House with a large car park. From there, a walk of two to three minutes along a path with few steps brings you to the Okama viewing platform. The rest house has a shop and a restaurant.

By car, it takes about an hour from Yamagata City via the Echo Line and High Line. In season there are also buses from Yamagata Station and from Shiroishi-Zao Station on the Miyagi side, but they run very rarely, so check the timetable in advance. There is also a hiking route: ride the Zao Ropeway up from Zao Onsen on the Yamagata side and walk from the summit station.

Tips

  • Even in summer it can be cold and windy at the top. Bring an extra layer and wear comfortable walking shoes.
  • When fog rolls in, Okama can disappear from view completely. For peace of mind, check "Today's Okama" on the Miyagi Zao Eboshi Resort website to see the day's visibility before you set off.
  • According to the Japan Meteorological Agency, volcanic gas is being emitted in parts of the Umanose caldera where Okama lies. Stay out of restricted areas and leave immediately if you notice anything unusual. Check the agency's volcano information before you go, too.
  • Autumn leaves are at their best from late September into October. The winter road closure begins in early November, so if you are going in autumn, plan early.

Sources

Updated 30 September 2026. Opening hours and prices change, so check the official site before you go.

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