Ryusendo, one of the three largest limestone caves in Japan, sits in the mountains of Iwaizumi, less than 15 kilometers from the Pacific Coast of Iwate Prefecture. An underground river pours out of the mouth of the cave, perhaps leading to its name, “cave of the dragon’s spring”. It is a designated National Natural Treasure, and with good reason.

The cave is so large that it is still being explored nearly a century after formal surveys first began. It is at least five kilometers long, but also has substantial vertical portions, including at least eight known underground lakes, the deepest of which is 120 meters (the deepest underground lake known in Japan). There are also other, smaller pools, deep water sections of the river, including the “pool of long life” just inside the mouth of the cave. (Farther into the cave, there is a “spring of long life”, too.)

Only about 700 meters of the cave is currently open to visitors and, thanks to the river running through the cave, much of that open area requires visitors to traverse catwalks suspended above the flowing water. In some places, atmospheric submerged lights allow visitors to see the river’s crystalline waters.

After passing through a straight and narrow natural passageway (actually a natural fault line), you enter the first chamber, with its high, cathedral-like, ceiling. This cave is home to five different species of bat and if you look up as you pass through, you’ll spot them, sleeping away their day. Nocturnal creatures, the bats leave the cave after dark to hunt insects. How they know when night comes is anybody’s guess. Maybe because someone turns off the lights after all the human visitors go home?

Deeper into the cave, the path forks, although either choice ultimately leads to the same high-ceilinged chamber, known as “The Imperial Palace”. You are on solid ground at last, the river somewhere below your feet.

In keeping with the local myths and legends surrounding the cave’s history, rock formations with weird, evocative names, including stalactites and stalagmites, are labelled all along the way. One formation looks like a Jizo, others include a guardian lion-dog, a turtle, and a “silent waterfall” of stone, with red mood lighting.

As you traverse The Imperial Palace, you are ascending and at the end of the chamber there is another fork. Head downward to reach the lakes or climb up to the highest point in the cave, some 10 stories above the water level of the lakes. It’s a circle route, either choice ultimately passes by both.

The deep lakes, with more submerged lights giving some idea of their depth and the clarity of the water, are perhaps most striking to see.

At the same time, on the upper path, at one point there is an observation deck suspended into a vertical chamber high above one of the underground lakes. Look over and down, if you dare.

Most caves, especially those that extend deep into mountains, are known for their constant temperatures. Ryusendo is no exception. It is a constant 10C/50F, a rather cool temperature, even for a cave. A sort of emergency exit tunnel has been drilled through the mountain at one point. It is now being used by visitors to exit as traffic through the cave is currently “one-way” only, part of measures to prevent the spread of COVID-19.

The man-made tunnel is also home to cabinets filled with bottles of “Ureira”, a wine made from wild grapes grown in this Iwaizumi area, stored here at this constant temperature while the wine ages. Look for it at the shop across the road from the cave entrance.

Hours: 10:00 am to 4:00 pm (these are currently shortened hours due to COVID-19)
Admission: JPY1,100 (adults); JPY550 (children)

Getting there: As with anyplace in regional Japan, the remote cave is easiest to access by private car. However, there is also bus service. From Morioka Station, there is JR Tohoku bus service every couple of hours (135 minutes; JPY2,710, no charge if using any JR Rail pass). From Miyako Station, 35 minutes by Sanriku train to Omoto and then 25 minutes by bus (JPY1500). As both services are infrequent, visitors are advised to check schedules in advance and make an early start.

© 2020 Jigsaw-japan.com and Vicki L. Beyer
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