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Clear, bright blue underground lake lit from below inside Ryusendo Cave
Photo: Vindlys, CC BY-SA 4.0, via Wikimedia Commons
Iwate · nature

Ryusendo Cave

龍泉洞

A cave in Iwaizumi, Iwate, counted among Japan's three great limestone caves, where you can gaze into clear underground lakes of a blue known as "Dragon Blue".

Entrance building of Ryusendo Cave at the foot of a rocky cliff
Photo: Iw ke (talk), Public domain, via Wikimedia Commons
Clear water welling up among rocks inside the Ryusendo caves
Photo: Mamusi Taka, CC BY-SA 3.0, via Wikimedia Commons

One of Japan's three great limestone caves

Ryusendo is a shonyudo (a limestone cave, formed as water slowly dissolved the rock over a very long time) in the town of Iwaizumi, Iwate Prefecture. Along with Akiyoshido in Yamaguchi Prefecture and Ryugado in Kochi Prefecture, it is counted as one of Japan's three great limestone caves.

It was designated a national Natural Monument in 1938, and the bats living inside the cave are protected along with it. Its confirmed length is 4,088 m, of which about 700 m is open to visitors. Surveys are still going on, and the whole cave is thought to be more than 5,000 m long.

Clear blue underground lakes

The highlight is the underground lakes. According to the official website, eight underground lakes have been found in the cave, and you can see three of them. The water is extraordinarily clear, and its blue has been named "Dragon Blue". The Third Underground Lake is as much as 98 m deep.

In 1985 the water of the underground lakes was chosen as one of Japan's "100 Famous Waters" (100 places selected for the quality of their water). All around the cave you can also see stalactites that have formed over many years.

Ryusen Shindo Science Museum

Right next to Ryusendo is a separate cave, Ryusen Shindo, discovered in 1967. Remains left by people long ago have been found inside, and today the cave itself is open to the public as a science museum.

Getting there

The official website recommends coming by JR Bus from JR Morioka Station, which takes about 120 minutes from Morioka Station to Iwaizumi (Ryusendo). By car it is about 110 minutes from Morioka and about 60 minutes from Miyako.

When the water rises after heavy rain, the cave may be closed to visitors or the route may change. Check the announcements on the official website before you go, along with the opening hours and prices.

Tips

  • The temperature inside the cave is about 10°C all year round. Bring something to put on, even in summer.
  • After prolonged rain the cave may close because of high water. It also closed temporarily after typhoon damage in 2016 and 2024.
  • It takes about 2 hours each way from Morioka. Check the bus timetable on the official website, and on a day trip, plan around the time of the last bus back.

Sources

Updated 28 September 2026. Opening hours and prices change, so check the official site before you go.

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