Tachikawa Walk: Slopes, River Terraces and a Flat City’s Hidden Tilt

Where the Tamagawa Aqueduct “climbs a slope” downstream: Sunagawa Sanban and the built-up bank

Water flows from high places to low ones. You learn that in elementary school. Yet in Tachikawa there is a waterway where the land is higher downstream.

The city’s guide to the Tamagawa Aqueduct, listing the highlights in the city from upstream to downstream, slips in, quite casually, “Sunagawa Sanban, where the terrain is higher downstream.” When I first read it, I suspected I had misread.

The explanation was in issue 6 of the same Tachikawa Monogatari. Below Mikage Bridge, it says, the land along the aqueduct gets higher downstream because of the river terraces. So a bank was built up on the upstream side. The place names around here are Tsukidote-muko (“beyond the built bank”), Dote-shita (“below the bank”), Dote-muko (“beyond the bank”) and so on.

The aqueduct itself did not climb a hill. Its bed, naturally, slopes downstream. It was the surrounding ground that, because of the terraces, got higher the further downstream you went. So a bank was raised on the lower, upstream side to keep the waterway at its height. The people of Edo, working against the lie of the land, reshaped their water channel into a single gentle slope. The place names still describe the work today. Beyond the bank they built: “beyond the built bank”. Below the bank: “below the bank”. The names serve in place of a construction record.

Running a waterway that drops only a little over 2 metres per kilometre for 43 kilometres. The tilt of Tachikawa’s land is more than three times the aqueduct’s gradient. If the land always tilted in the direction the water flowed there would be little trouble, but at the edges of the terraces, places appear where it does not. The bank at Sunagawa Sanban must be where the accounts were balanced. I could not, this time, find a document that gives how high a bank was raised in the 1653 construction.

Sunagawa also keeps memories of life on a dry plateau. Issue 4 of Tachikawa Monogatari says the Musashino Plateau areas, Sunagawa among them, were covered with volcanic-ash soil that was hard to farm and had few water sources, so they were almost untouched until the beginning of the Edo period. Settlement began, it says, with one of the old wells of the type called maimaizu-ido — “snail wells” — dug around Sunagawa Sanban: wells dug in a spiral down into the ground until at last they reached water. In Shibasaki in the south, water springs from the foot of the cliff; in Sunagawa in the north, you meet water only after digging round and round into the earth. Within one city, the distance to water differs this much. (More in our Tamagawa Aqueduct and Sunagawa article.)

Living on the edge of the terrace: springs, a Jomon village and a Showa-era boy

The edge of the cliff has long been a place where people lived.

The history newsletter says the edges of river terraces were sunny and well drained, with rivers and springs at the foot of the cliff, making them very pleasant places to live in an age without water mains, sewers or heating. Of the 21 archaeological sites confirmed in Tachikawa, many line up along the southern escarpment. Rain that falls on the plateau and soaks in comes out as springs at the foot of the cliff and becomes streams. The Jomon people seem to have made their base on top of the plateau and gathered food below the cliff, rich in greenery and water.

At one of those sites along the escarpment, the Mukogo site, there is a rather delightful story. According to issue 6 of the newsletter, from about 1970 to 1977 a boy, then in elementary and junior high school, dug up pottery and stone tools at the Mukogo site, washed and sorted them carefully, and organised them by writing the date and place of each find in poster paint. The collection was donated to the city in 1982 and is now kept at the city’s Museum of History and Folklore. The newsletter marvels that it is hard to believe an elementary or junior-high pupil did it alone. At the same age, the most I dug was the sandpit in the schoolyard. (See our article on the museum.)

What did the area around the escarpment look like when the boy was digging up his pottery?

Then: a photograph of Shibasaki-cho around 1940, in the same issue, shows trees in a single line along the escarpment, houses on the plateau above, and rice paddies spreading across the lowland below the cliff. The Nekawa had a boat landing until the mid-1950s, with a teahouse by the jetty. The irrigation channel that drew water from the Nekawa to the paddies below the cliff was cleaned every year on 1 May by all its users together, but in the first half of the 1970s it could no longer draw water and fell out of use.

Now: the paddies below the cliff have become housing, and the Nekawa has become a green path. Still, the newsletter writes, the steep cliff that runs from around Shibasaki-Taiikukan Station conveys the long history of the Tama River cutting into the plateau. Ride the Tama Monorail from Tachikawa-Minami towards Shibasaki-Taiikukan and you can see the town suddenly drop a step beyond the window. The paddies are gone, but the step is not. (For the green path, see our Nekawa and Tama River article.)

The cliff did not give only blessings. Issue 12 of the newsletter adds that the edge of the cliff, though rich in water sources, was also prone to flooding. Along the escarpment stand a scattering of small shrines — Dairokuten Shrine, Sawa no Inari, Takitsubo Benten, Yagawa Benten. Places to give thanks for the gift of water were also places to fear it. The mound on which Sawa Inari stands is thought to be a burial mound of around the 6th or 7th century, according to the city’s walking-route guide. The edge of the cliff is a place where people have been leaving their prayers for far more than a thousand years.

Around the Tokyo Metropolitan Agriculture and Forestry Research Center in Fujimi-cho, Musashino’s mixed woodland still survives on the escarpment, and spring water can be seen coming out of parts of the cliff. Tachikawa City has chosen it as one of its “Twelve Green Views”. One of the twelve green landscapes the city picked is the cliff itself.

The cliff of the “Tachikawa Fault”: what made it?

Finally, the story of the 4.5-metre cliff.

Of all the stories about Tachikawa’s ground, the best known is probably the Tachikawa Fault. The government’s Headquarters for Earthquake Research Promotion assesses the Tachikawa fault zone, about 33 kilometres long, running from Naguri in Saitama Prefecture through Tachikawa to Fuchu. The evidence has been a step that runs straight from northwest to southeast across the Musashino Plateau. A national supplementary survey report sums it up: if it is regarded as a scarp made by fault movement, a gentle scarp no more than 8 metres high and 100 to 300 metres wide continues along it.

That scarp is in the city centre too. A national intensive survey report says that in central Tachikawa there is a cliff landform about 4.5 metres high, lower on its west side, though its exact position is unclear. Around Izumi-cho, where the city hall stands, an offset of 4.5 metres had been estimated.

But the national intensive survey carried out from fiscal 2012 to 2014 reached an unexpected conclusion. South of Mitsugi in Musashimurayama, all the way to the Tama River, no geological evidence was found that this cliff had been made by fault movement. Probing underground with sound waves and gathering old boring records, they found no offset in the buried strata to match the cliff’s height. The report recognised only about 12 kilometres, from Kanekodai in the north through Hakonegasaki to around Mitsugi, as an active fault, and gave it a new name: the “Hakonegasaki Fault”.

Partway through the survey there was also a commotion that filled the news. According to reports at the time, in March 2013 the stones that the survey team had cited when announcing that it had “confirmed a new active fault” turned out to be lumps of concrete, and part of the announcement was withdrawn. The site where they had dug a huge trench was the former Nissan Motor Murayama plant in Musashimurayama. Man-made objects from underground had been wearing the face of a fault. The researchers’ bitter experience speaks plainly of how hard it is to read the ground.

So what made the 4.5-metre cliff in central Tachikawa? If not a fault, then a river, the wind, something else? The report goes no further than saying there is no positive evidence for interpreting the cliff as a scarp made by fault movement. The answer is not in yet.

There is one thing, however, that must be said. The Headquarters for Earthquake Research Promotion’s page still lists the Tachikawa fault zone as a zone of about 33 kilometres. The national assessment has not been rewritten. Tachikawa City, too, includes an earthquake on the Tachikawa fault zone among the scenarios in its regional disaster-prevention plan. Not knowing what the cliff really is, and not needing to be prepared, are two different things. (See our disaster-prevention article.)

At Hakonegasaki in the north there is a pond made by the fault. The supplementary survey report describes Sayama Pond in the town of Mizuho as a fault lake. The stream that flows out of Sayama Pond is the Zanbori River, which passes west of Showa Kinen Park and cuts down through Tachikawa from north to south. Water from a fault pond flows past a cliff that may or may not be a fault, and into the Tama River. Tachikawa’s ground has not yet told us everything about itself.

Tachikawa as a town of slopes: what flatness and cliffs have made

Having walked this far, I return to the opening questions.

Why does Tachikawa lean? Because it lies partway down the gentle slope of a plateau that spreads like a fan with Ome at its apex. From Nishisuna-cho in the northwest to Nishiki-cho in the southeast, an invisible slope falls 7 to 8 metres per kilometre.

Why are there slopes only north to south? Because the cliffs of the terraces the Tama River left uncut in a cold age about 20,000 years ago run east to west. Walk alongside a cliff and it is flat; only when you cross one does it become a slope.

That answers half. The other half is still underground. Who made the 4.5-metre cliff in the city centre? How high was the aqueduct’s bank at Sunagawa piled?

Still, one thing has become clear. Tachikawa’s flatness was not just “nothing there”. Because it was a vast, flat plateau, an airfield was placed here, and the town became the capital of the sky. Because there was a cliff on the plateau’s southern edge, Jomon people built a village, Shibasaki village was born, and cherry trees bloomed along the Nekawa. Having both flatness and cliffs became the skeleton of the town of Tachikawa.

Stand on top of the cliff and the Tama River lowland opens to the south, and the sky becomes one size bigger. In central Tokyo, you learn the differences in height from slopes in the canyons between buildings. In Tachikawa, you learn them from the size of the sky.

Answer to the quiz

The answer is (A), east–west. According to the city’s history newsletter, the escarpments of the terraces made by the Tama River run almost exactly east to west, so moving east or west you hardly feel a slope, while moving north or south you meet a proper slope at a certain point. The exceptions, it says, are Wakaba-cho and Saiwai-cho, because the Kokubunji escarpment lies to their east.

Before you go

• Walking the slopes of the Tachikawa escarpment: the city’s walking route “Walking the Old Villages” starts from the South Exit of JR Tachikawa Station and takes in Suwa Shrine, Fusai-ji Temple, the Sanchu-zaka Jizo hall and the Museum of History and Folklore — a route that goes down and up the slopes between the tops and feet of the terraces (the escarpment is a walk of a little over ten minutes south of the station). Route (Japanese): https://www.city.tachikawa.lg.jp/kanko/bunka/1004244/1004848/1004889.html — see also our Old Villages article.
• Woodland and springs on the escarpment: the Tachikawa escarpment around the Tokyo Metropolitan Agriculture and Forestry Research Center (Fujimi-cho) is one of the city’s “Twelve Green Views”: https://www.city.tachikawa.lg.jp/koenryokuchi/kurashi/kankyo/mizutomidori/tachikawa/tachikawagaisen.html
• Around Kaigara-zaka: near the Nekawa Kaigarazaka Bridge at the end of the Nekawa Green Path. The city’s walking route “From Yagawa towards the Tama River” starts at JR Nishi-Kunitachi Station and takes in Yagawa Ryokuchi, the Nekawa Kaigarazaka Bridge and the Nekawa Green Path: https://www.city.tachikawa.lg.jp/kanko/bunka/1004244/1004848/1004890.html
• The aqueduct that is higher downstream: around Sunagawa Sanban, below Mikage Bridge; the nearest station is Musashi-Sunagawa on the Seibu Haijima Line. The city’s guide to the aqueduct’s highlights: https://www.city.tachikawa.lg.jp/kanko/bunka/1004244/1004847/1019994/1004854.html
• Check the heights yourself: on GSI Maps (Chiriin Chizu), tap the map and the elevation of that spot is shown: https://maps.gsi.go.jp/
• Cycling north: according to the local paper’s advice, the escarpment slopes get gentler the further east you go. On foot, take care partway up some slopes, where traffic can be heavy.
• From central Tokyo: Tachikawa Station is reached from Shinjuku on the JR Chuo Line without changing trains. Carry an IC transport card such as Suica or PASMO; it works on JR, the monorail and Seibu trains.
• Etiquette: the escarpment’s shrines are places of worship — keep your voice down — and many homes stand along the cliff; stay on public roads and paths.
• Putting it together: the springs below the cliff lead on to Yagawa Ryokuchi (Yagawa and the hake), the green path below the cliff to Nekawa and the Tama River, and the aqueduct to the north to the Tamagawa Aqueduct and Sunagawa.

When you reach the top of the slope, at the North Exit of Tachikawa Station

Tachikawa’s slopes turn flat when you reach the top. The road from the southern escarpment back to the station is also a road that climbs one step. After a slope, the flat road always feels longer than you expect.

One minute’s walk from the North Exit of Tachikawa Station — in Akebono-cho, a little over 83 metres above sea level — on the third floor of the Etoile Building at 2-14-10 Akebonocho, Tachikawa, is On the Shore Tachikawa (オンザショア立川店), a hot yoga studio heated by lava-stone plates. As well as lava-stone hot yoga, it offers room-temperature yoga, Pilates, women-only kickboxercise, boxercise, HIIT and personal training, with more than 25 kinds of yoga lesson.

It is open every day from 8:00 to 23:30, the same hours whatever the day. Walk the escarpment in the morning or roam the plateau until evening, and there is still time to drop in.

A trial yoga lesson costs ¥1,980 including tax, with two bath towels, one face towel and a yoga mat included in the rental. You can call in on the way back from your walk with nothing but yourself.

Pregnant guests cannot take part in lava-stone hot yoga, but room-temperature maternity yoga is available.

Many of our yoga instructors speak English, and the studio’s owner, Naomi Fujita — who holds Eiken Grade 1, Japan’s top English qualification, and a perfect TOEIC score, worked as a translator and overseas interpreter at Nomura Securities, and lived in Alaska for three years — often helps guests from the US bases in English herself. Overseas guests have praised the English support in their Google reviews. If you would like help in English, just mention it when you book.

Studio information: https://ontheshore.jp/ — prices: https://ontheshore.jp/price/ — trial lesson booking: https://site.locaop.jp/C0aVK?_src=hp

Down the steps cut by a river 20,000 years ago, and back up again — then, on the same legs, to the third floor of a building. The newest step in Tachikawa is probably this staircase.

Cover photo: The greenery of Showa Kinen Park on Tachikawa’s flat plateau, with distant mountains and Mount Fuji. (Photo: Nishifutsu / CC BY-SA 4.0 / Wikimedia Commons)

Information as of October 2026.

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