伊尾木洞

Ioki do - Ioki Cave


Useful Information

Location: 117, Ioki, Aki City, Kochi Prefecture.
East of Aki City, off National Highway 55.
(33.491273, 133.933227)
Open: Closed during high water level.
Guided tours: Reservation one week in advance required.
[2022]
Fee: Self Guided: free.
Regular Course: Adults JPY 800, Children (6-11) JPY 300, Children (0-5) free.
Adventure Course: Adults JPY 1,000, Children (6-11) JPY 300, Children (0-5) free.
Groups (11+): Adults JPY 700.
[2022]
Classification: SpeleologySea Cave ExplainKlamm
Light: bring torch
Dimension: L=40 m, W=3 m, H=5 m.
Guided tours: self guided, L=800 m, D=20-50 min.
Regular Course: L=800 m, D=40-60 min.
Adventure Course: L=1,200 m, D=70-90 min.
Photography: allowed
Accessibility: no
Bibliography:  
Address: Aki Tourism & Information Center, 117, Ioki, Aki City, Kochi Prefecture, Tel: +81-887-34-8344.
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.

History

1915 declared a National Natural Monument.

Description

伊尾木洞 (Ioki Cave) is not really a show cave, and it is not only a gorge. We had real problems to classify this site, and we almost classified it as a gorge. But it is both.

Separated from the sea by 350 m of coastal plain below 10 m asl, is a sort of escarpment, which is an ancient coastline. Its unclear if the sea retreated or the land uplifted, in Japan both is likely. But the escarpment is 45 m high and followed by a second coastal plane about 55 m asl. A river falls down a waterfall at the end of this plain into a gorge, which is cut deep into the plain, flows through a narrow gorge, through a 40 m long cave, and finally through the coast plain to the sea. So we have a waterfall, a gorge, and a cave. Quite astonishing is the fact that the cave was not formed by the river, it is a sea cave which formed together with the ancient cliff line.

The site is entered at the lower end, a trail was built along the river for 200 m. You can walk about 500 m to the waterfall and back, through a green gorge which was dubbed correctly Green World by the local Tourist Office. A thick carpet of mostly tropical ferns, more than 40 species, covers the walls. Just to name a few, Asplenium capillus, Adiantum capillus, Neocheiropteris, Neocheiropteris, Hagoromo fern, Shiroyama Zenmai, and Woodwardia orientalis. This extreme diversity was the reason why the site was designated a National Natural Monument.

In front of the site, at the National Highway 55, is a parking lot and the Ioki Cave Tourist Information Center. It serves as ticket office and pamphlets of Ioki Cave, also free rental gumboot. But it also offers tourist information on the surrounding area and free Wifi.