Subterranean beauty shows up above ground

The Yomiuri Shimbun

Nagatoro’s Iwadatami continues along the river. Thin layers were made underground at a depth of 20 kilometers to 30 kilometers.

By Kazuhiro Katayama / Yomiuri Shimbun Senior WriterNAGATORO, Saitama — After I passed through the ticket gate of Nagatoro Station, crossed the train tracks and walked through a small shopping area, a riverbed opened in front of me.

The river was flanked by huge rocks and a forbidding cliff wall. I recognized the view from a photo I’d seen in which it appeared to be deep in the mountains, but it’s so close to the train station I was a little surprised.

The rocky area, called Iwadatami, consists of many thin layers of rock, creating complicated rises and falls. Anywhere a tourist sits, it looks like a natural bench.

As I walked through the Iwadatami landscape for 600 meters along the Arakawa river, a rubber boat with five or six people came down the river. Rafting here is popular among young people. Shouting merrily as they rowed, they even cheerfully jumped right into the water at the instruction of the guides.

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  • The Yomiuri Shimbun

  • The Yomiuri Shimbun

    The preserved Historic Arai Silkworm House, a sericulture farmhouse from the Edo period (1603-1867)

As I watched, I felt like I wanted to go out on a boat. However, I’m not merry enough to jump into the water while rafting, so I decided to ride a poling-boat down the river. It’s about a 20-minute course, which began further upstream and arrived back at Iwadatami. Boatmen stand in the bow and the stern and skillfully steer with bamboo poles.

Heavy rain had fallen the day before, so the water in the river was muddy. “Usually you can see the bottom even in deep areas,” one of the boatmen told me. The stream was calm, and I enjoyed the view of Iwadatami, where I had been standing shortly before, and of the cliff on the other side of the river.

Hodosan Jinja shrine is located on the opposite side of Iwadatami across the station. It’s one of the so-called Three Chichibu Shrines and has been worshipped throughout the Kanto region for a long time.

After visiting the shrine, which is decorated with colorful sculptures, I climbed Mt. Hodo by ropeway, and visited another part of the shrine in a quiet forest. The mountain is less than 500 meters above sea level and not so high, but the view is good and it’s possible to see several kinds of flora, such as azalea and robai Japanese allspice trees.

It’s about one kilometer from Nagatoro Station to Hodosan Jinja shrine. Even on the short way to the shrine, there are many places to visit such as the Historic Arai Silkworm House, a local museum, and Asamireizo, a shop famous for making shaved ice using natural ice.

Scientific significance

Iwadatami is not the only scenic spot with strangely shaped rocks, but it’s also said to be a valuable place for geological studies.

“The land was pushed underground to a depth of 20 kilometers to 30 kilometers due to crustal movement, and became crystalline schist due to strong pressure. It ultimately emerged again; that is Iwadatami,” said Motoko Inoue, a curator of the Saitama Museum of Natural History.

“You can see phenomena that occur deep underground, so it’s also called ‘the window of the Earth.’”

Since the Meiji era (1868-1912), many geological scholars have engaged in research about Iwadatami. Kotora Jinbo, who taught at Tokyo Imperial University, wrote, “The geologists of our country must visit at least once in their lives.”

A stone monument, on which is carved words stating “This is the birthplace of Japan’s geological studies,” proudly stands in front of the museum.

At the same time, Iwadatami is a treasure house of various insects and plants, including dragonflies. The museum distributes walking maps showing recommended places to visit for each season. “The middle and end of November is the season for autumn colors. In autumn and winter, when the weeds are withered, it’s also great for us to observe Iwadatami,” Inoue said.

I’m not a geologist, but I was never bored walking in Iwadatami, seeing landscapes full of variety.

Close proximity

Many tourist sites are located within walking distance from Nagatoro Station.

The Mineral and Plant Specimen Gallery, the predecessor of the Saitama Museum of Natural History, opened in 1921, and the whole Nagatoro area was designated as a place of scenic beauty and natural treasure in 1924. It has a long history as a tourist destination, but it’s not old-fashioned, and there are many young people on weekdays.

It’s possible to make a day trip from Tokyo, and can be reached on foot from the station. It’s a perfect place to visit when you suddenly have a day off and feel like going out.


From Ikebukuro Station, it takes about 80 minutes to Seibu Chichibu Station by Red Arrow limited express train on the Seibu Ikebukuro Line. It’s about 20 minutes from Ohanabatake Station to Nagatoro Station by the Chichibu Railway.

For more information, call the Nagatoromachi Tourist Association at (0494) 66-3311.

To find out more about Japan’s attractions, visit

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