Discover Ryusendo Cave and Its “Dragon Blue” Underground Lakes

Why MAKES RYUSENDO CAVE SO SPECIAL?

Nestled deep within the mountains of Iwate Prefecture, Ryusendo Cave is one of Japan’s three great limestone caves. It’s believed to stretch for nearly 5 km (3.1 miles) into the mountains, though only around 4 km (2.5 miles) have been explored since surveys began in the 1920s. Roughly 700 meters (2,297 ft) of the cave is open to the public¹.

Ryusendo Cave is celebrated for its underground lakes. Deep within the cave system, vast amounts of crystal-clear blue water flow through an underground river, feeding four subterranean lakes hidden beneath the mountains of Iwate.

Visitors can view three of these lakes, which measure 35 meters (114.8 ft), 38 meters (124.7 ft), and 98 meters (321.5 ft) deep. Lit by powerful underwater lights, their otherworldly clarity and vivid sapphire-blue color are what make Ryusendo so famous.

Situated further into the cavern system, the fourth lake isn’t open to the public. At 120 meters (393.7 ft), it’s the deepest recorded underground lake in Japan¹.

Visiting RYUSENDO CAVE

Ryusendo Cave is located in the mountains of Iwaizumi Town, a little over two hours east of central Morioka. It’s in the middle of nowhere, with limited bus departures, so a day trip from Morioka – the closest major transport hub – requires some advanced planning and at least half a day.

A visit to Ryusendo will actually take you to two caves – the main cave and a smaller adjacent cave that functions as a science museum. It’s believed that these two caves were once connected and part of the same cave system². It’ll take the average person roughly two hours to visit both caves.

Pictured below is a copy of the map they give you upon entry. The caves can be explored via a well-developed network of pathways, stairs, and bridges.

As of May 2026, admission to both caves is JPY 1,100 per adult.

RYUSENDO CAVE

I may not be as fascinated by caves as some people, but entering one for the first time rarely fails to impress. Shortly after walking into the cave, you’ll go through this section called the Skyscraper. It’s an area known for its high, cathedral-like ceiling.

Formed along a geological fault, you’ll then go through this long section known as the Extended Passageway or the Dragon’s Passage. Ryusendo Cave is amply lit and well-maintained, so it’s easy to navigate throughout.

This was one of the most visually striking parts of the cave. What you’re looking at here is the First Underground Lake, but viewed from an observatory accessible via an elevated staircase. The red lanterns are suspended by wires for dramatic effect.

Note the intense blueness of the water, often described as a “dragon blue”. These underground lakes are fed by groundwater from the forested area north of Ryusendo Cave.

I didn’t see any but the cave is home to several varieties of bats, including rare and protected species. Your best chance of seeing them is from the Bat Spot, a lookout point near this observatory.

This passage is known as the Moon Palace, a section of the cave where the limestone walls resemble a lunar-like world.

The stairs and pathways inside the cave are even and well-maintained, but they do get wet, so it’s important to wear appropriate footwear.

I didn’t find any section of the cave particularly challenging to get through, but you will climb a total of 274 steps. Guests who aren’t comfortable have the option of doubling back, though people with moderate levels of fitness shouldn’t have any difficulties.

This is the Second Underground Lake. Discovered in 1962, it’s known for its remarkable clarity, which allows guests to see far into its depths. The rich and vibrant blues of these lakes really are mesmerizing.

This is the Third Underground Lake and the deepest of the three accessible lakes. It has a recorded depth of 98 meters (321.5 ft), roughly equivalent to a 30-32 story building!

The temperature inside the cave stays below 10°C (50°F) year-round, making it an ideal place to store sake. This sake cellar is accessible only during peak seasons and the winter festival.

The sake cellar leads to this limestone tunnel. People visiting Ryusendo Cave in the off-season will need to do a loop back and exit the cave via the main entrance. In peak seasons and in winter, you’ll have the option of exiting through this tunnel.

RYUSENSHINDO SCIENCE MUSEUM

Located across the Shimizu River, just a short walk from Ryusendo Cave, is the Ryusenshindo Science Museum. When I read about a museum near Ryusendo, I expected a typical room in a building with exhibits about the cave. Never did I expect that the museum would be in another cave.

Upon entering the museum, you’ll descend into this tunnel with a few mildly interesting exhibits displayed along the walls.

I’ve never seen a museum situated inside an actual cave, so I thought that was pretty cool. As previously mentioned, it’s strongly believed that this cave used to be connected to the larger Ryusendo cave complex.

Inside the cave museum, you’ll find interpretive panels explaining the cave’s formations and the geology behind them. To the untrained eye, these rock formations can start to look pretty similar after a while, so the informational panels help you better understand and appreciate what you’re seeing.

Without looking it up, can you confidently describe the difference between a stalactite and a stalagmite?

I like amphibians so it was cool to learn to learn about the types of salamanders that call Ryusendo home.

Turning a corner, this diorama nearly made me jump off the platform. The Japanese couple behind me reacted in the same way too. Ha!

Apparently, remains from the Jomon period have been discovered in this cave.

Visit Ryusendo Cave FAQs

Is Ryusendo Cave worth visiting?

Yes, I think so, and that’s coming from someone who isn’t that interested in caves to begin with.

Well-maintained and easy to navigate, going through the cave was a breeze, and seeing the underground lakes was quite cool. It’s also big enough to justify the 4+ hours of bus travel between Morioka and the cave.

Would I still have made the trip if transportation hadn’t been covered by the JR East Pass? Probably not. As of May 2026, the one-way trip costs JPY 2,710. Not exactly cheap!

Which passes cover transportation to Ryusendo Cave?

Aside from the JR East Pass, the trip between Morioka Station and Ryusendo Cave is fully covered by the Japan Rail Pass.

Are there luggage lockers at RYUSENDO CAVE?

Yes, there are coin-operated lockers at the tourist center. You can also store your luggage in lockers at Morioka Station, which is what I did.

Is there a place to eat near Ryusendo Cave?

Ryusendo Cave is in the middle of nowhere, so I was worried about not having anything to eat. Thankfully, there’s a small restaurant at the tourist center that serves simple meals like this kaki (oyster) fry set. Oishi!

THE FINAL SAY

Even as someone who isn’t particularly fond of caves, I still wound up enjoying my visit to Ryusendo. I’ve been to bigger caves with more impressive rock formations, but Ryusendo’s underground lakes are genuinely mesmerizing. Their impossibly clear blue waters can’t adequately be captured in photos.

If you have a JR East Pass (or a Japan Rail Pass) and have extra time in the Tohoku region, I think Ryusendo is absolutely worth considering. It’s a chance to explore a more remote side of Iwate Prefecture and see one of Japan’s three great limestone caves.

But if you don’t have either rail pass, are short on time, or simply don’t have much interest in caves, then you may want to spend your time (and money) elsewhere.

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References

1. Experience the miraculous underground “Dragon Blue” lakes. Travel Japan.
2. Ryusen Shindo Science Museum. Ryusendo.