Akka Cave - Akkado Cave

Useful Information

Entrance of Akkado. Public Domain.
Location: Iwaizumi-tyo, Iwate. 600 km north of Tokyo.
Open: Mid-APR to JUN 9-16.
JUL to AUG 9-16:30.
SEP to NOV 9-16.
Fee: Adults JPY 1,000, Children (6-15) JPY 600, Children (0-5) free.
Groups: Adults JPY 850, Children (6-15) JPY 500.
Classification: SpeleologyKarst cave
Light: LightLED Lighting
Dimension: L=23,702 m, VR=280 m, T=8 °C.
Guided tours: L=1,000 m, D=30 min.
Address: 安家洞 - Akkadō, 161−1 Akka, Iwaizumi 027-0611, Tel: +81-194-24-2011, Mobile: +81-90-4313-7101. E-mail:
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


Speleothems of Akkado. Public Domain.
1959 first explored by the Japan Cave Groundwater Research Group after a visit to Ryusendo cave.
1980 designated as a Natural Monument.
1991 cave opened for cave trekking tours on two routes during summer.
1997 a total length of 12.7 kilometers published.
20-MAY-2006 new survey with 24 km presented on the Meeting of the Japan Association of Groundwater Hydrology at the University of Tokyo.
SEP-2013 part of a Japanese Geopark.
2015 opened as a show cave.


安家洞 (Akkadō - Akka Cave) is Japan's longest cave. It is located in Iwaizumi, a town with 12,000 inhabitants in Iwate Prefecture, northeastern Japan.

The cave was explored since 1997 by the Association for Cave Exploration, a caving club based in Chiba near Tokyo. It has already been the longest cave of Japan before, with a total length of 12.7 km published in 1997. During the next ten years the caving club explored and surveyed a lot of new passages. Finally the cave totaled almost 24 kilometers.

Akkado is a maze-like cave, which explains the big length. A part of the maze is water filled, which forms an underground lake. The lake extends two kilometers from north to south and 500 meters from east to west. The water is up to 140 meters deep.

The first 500 m of passage from the entrance are now open to the public. The tour goes in and returns the same way. Visitors are equipped with helmet, boots and a jacket, which is a little ridiculous as this is a well developed show cave with paved trail and electric light.