Shirokane Bunsui（白金分水）June 28, 2025
I had no idea there was so much nature hidden in the middle of such an upscale neighborhood.
Where I Walked
During this walk, I was able to encounter layers of history from different eras.
The Shirokane Bunsui is a small branch stream that once diverted water from the historic Mita Irrigation Canal.
Originally used for agricultural and domestic needs, this channel now quietly winds through a residential area in Shirokane.
The building with the large red sphere is a driving school.
This area sits on a plateau, where the Mita Irrigation Canal once flowed, bringing water as part of an old aqueduct system.
A small valley lies beneath the point where the Yamanote Line passes over the Yamanote Freight Line.
Near the Chojamaru railroad crossing—where the Yamanote Line passes over the Yamanote Freight Line—it’s said that water from the Mita Irrigation Canal used to be diverted into the Shirokane Waterway.
The name “Chōjamaru” combines two elements: “Chōja,” (長者) meaning a wealthy or prosperous person, and “maru,” (丸) a suffix often used in place names or for ships and castles.
According to local lore, this area was once home to a very rich landowner — perhaps the wealthiest person in the village — and the name reflects that legacy.
Compared to a straight, sterile road, the gentle meandering of an old buried stream feels much more comforting — it has that true ankyo charm.
The waterway runs along the base of the cliff below Ebisu Garden Place.
It veers off to the right from the road and slips between houses.
I found a side path that leads right up to the waterway — but just like the gate I saw earlier, there’s another one here on the opposite end, making it impossible to pass through.
The gate I saw earlier, now viewed from the opposite side.
I walked downstream.
The old waterway is now hidden beneath a concrete cover.
It's a dead end ahead.
I’ve marked the section that’s not passable on the map.
Here begins another section where the path is blocked off.
Seen from downstream, this is where the closed-off section ends.
Looking downstream at the same point. The canal seems to pass by the left side of the four-story apartment building ahead.
Because it’s built along the river’s course, the building may have a trapezoidal shape.
The waterway hits the expressway and continues flowing beneath it for a stretch.
The dense grove of trees visible in the back left of the photo is part of the forest in the National Museum of Nature and Science’s Institute for Nature Study.
It seems that a confluence with a stream originating there was once located around here.
Once I finish tracing the current waterway, I plan to visit the nature reserve.
From here, the river leaves the highway and begins to meander along a winding path.
I believe these might be stones from the old river embankment.
After following the winding path for a while, I came to a street lined with shops.
It seems the river once flowed along this shopping street.
A shop with a blue awning is a dry cleaner — perhaps another quiet clue that a river used to run through here.
While walking through the shopping street, I spotted a space below street level that looked like it might have once been a waterway.
This photo was taken from the same spot as the previous one, but facing the opposite direction.
There used to be many traditional kanban-kenchiku (signboard-style) shops like this, but they’re gradually being replaced by modern buildings.
I came across an old national flag platform.
Here's a brief explanation of its historical background.
In 1937 (the 12th year of the Shōwa era), Japan was entering a period of increasing militarism and nationalism.
As part of efforts to promote national pride and loyalty to the Emperor, many schools, public facilities, and community spaces installed flagpoles specifically for raising the Japanese national flag.
These installations, often referred to as “national flag platforms” (kokki keijōdai), were symbolic of the government’s push to instill patriotism among citizens, especially the younger generation.
After turning the corner where the old flag-raising platform stands and walking a short distance, I arrived at Tanuki-bashi (Tanuki Bridge), which crosses the Furukawa River — the lower stretch of the Shibuya River.
Here’s a brief summary of the history behind Tanuki-bashi.
The area near Tanuki-bashi (Tanuki Bridge) in Shirokane was once called Tanuki Soba, named after local legends of raccoon dogs (tanuki) said to appear or be buried nearby.
In the Meiji period, Yukichi Fukuzawa, founder of Keio University, often visited a soba shop near the bridge.
He eventually bought the land, turned it into a villa, and built a waterwheel there.
This “Tanuki-bashi Waterwheel” used water from the Shirokane branch of the Mita Irrigation Canal, and the income from milling rice helped support his students’ meals.
Part of this land later became Keio’s elementary school and the Kitasato Institute.
Fukuzawa also built another waterwheel nearby, which his sons later managed.
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You can see the outflow of the Shirokane Bunsui from Tanuki-bashi.
From here, I decided to head back upstream toward another source of the waterway — the Institute for Nature Study.
There’s a little door above the entrance — or at least it looks like one. What could it be?
The Institute for Nature Study is a peaceful nature reserve in central Tokyo, preserving a rare remnant of the city’s original ecosystem.
Once part of a feudal lord’s residence, it now offers walking paths through lush forests, wetlands, and meadows, providing a glimpse of Tokyo’s natural past.
Inside the woods, you can find an old earthen embankment (dorui “土塁”) — a remnant of the area’s past as a samurai residence.
It was built around 500 years ago during the Muromachi period by the legendary Shirokane Chōja (“白金長者”), a wealthy landowner whose name lives on in local folklore.
The embankment once served as a defensive structure and boundary marker.
Today, the dorui stands quietly among the trees, a trace of history hidden in nature.
Within the woods, you'll find several ponds and wetlands that serve as natural water sources.
I saw many maple trees, so I’d love to come back during the autumn foliage season.