*This article is based on survey information as of January 2026 and the latest urban planning theory.

1. Strategic Geometry: Why the "no" Shape?

The limits of the grid and the infinity of the spiral

First, we will analyze the uniqueness of Edo from the perspective of urban design. Generally, the defensive lines of a walled city are classified into two types: a concentric pattern known as the "outline style" and a parallel pattern known as the "connected wall style."

However, the concentric city model had one fatal flaw in urban planning."Limits to Growth"As a city grows, the moment its population exceeds the capacity of its outer walls, the existing walls become an obstacle and prevent further expansion. To expand, the city must destroy the walls and build a new closed system on the outside, at great expense.

The spiral structure adopted by Edo offered a highly dynamic solution: the moat, which began at the inner citadel, was dug outwards without closing the circle. This allowed for the seamless expansion of the defense line and residential areas without interfering with existing urban functions.

In fact, Edo's urban area organically expanded from the initial Chiyoda and Chuo ward areas to the outer periphery over time. It was this flexible structure that allowed the city to maintain its urban functions while still maintaining Hirokoji and firebreaks after the Great Fire of Meireki (1657). This was an extremely sophisticated system, similar to the "agile" expansion of modern software development.

The size of Edo compared to other major cities

How large was Edo's growth due to this highly scalable system? Comparing population data for major cities around the world in the 18th century reveals its remarkable scale.

The graph below shows the estimated population in the mid-18th century.

As shown in the diagram above, Edo was the world's largest megacity in both name and reality, far surpassing London on the eve of the Industrial Revolution and Paris just before the French Revolution. Of this one million people, approximately 500,000 townspeople, excluding samurai, lived densely in an extremely small area of just 20% (townspeople's land) of Edo's total area.

Normally, such overcrowding would lead to infrastructure breakdowns, food shortages, and the spread of infectious diseases due to filth, causing the city to collapse. However, Edo did not collapse. On the contrary, it continued to function as a clean and safe city.

What made this miracle possible was the "dual use of logistics and defense," which will be explained in the next chapter.

2. The Ambiguity of Infrastructure: The Fusion of Defense and Logistics

The most ingenious aspect of Edo city planning was its "multi-functionality," which allowed a single piece of infrastructure to have multiple functions. In particular, the use of waterways (moats and rivers) was so rational that it would impress even modern city planners.

Logistics network as an "aqua city"

In the city of Edo, waterways were equivalent to modern-day "highways," while land routes were equivalent to "general roads." Traffic flowed from the Tone River system via the Edo River and artificial canals such as the Onagi River to the Sumida River. From there, goods were transported to consumers through canals that ran like blood vessels.

The areas around Nihonbashi in Chuo Ward and the Onagigawa River area in Koto Ward can be considered the centers of this water transport system. Until it was reclaimed during the period of rapid economic growth in the Showa era, Tokyo was literally a "city of water."

Another thing worth mentioning is the establishment of resource circulation (circular economy).

In London and Paris at the time, human waste was dumped on the streets, causing serious social problems such as water pollution and infectious diseases like cholera. However, in Edo, the sewage generated in the city was transported by ship to nearby farming villages (Kasai, Gyotoku, Kawagoe, etc.) as valuable fertilizer (night soil), and the vegetables produced there were then transported back to Edo by ship, creating a complete recycling loop.

The canals, dug for defense, supported logistics and even ensured environmental sanitation. This system, which killed three birds with one stone, was what made Edo a sustainable city.

3. Recommendations for Toyako Town: Implementation of the Neo-Edo Model

Deciphering the terrain and updating the "urban operating system"

Now, based on the historical analysis we have done so far, let's connect our thinking to the contemporary urban development of Toyako Town, Hokkaido.

Toyako Town is a municipality with an overwhelming "center of nature" in the form of a huge caldera lake. This topographical feature is structurally similar to Edo Castle (the center of the void) in Edo. However, the current urban structure is limited to a collection of circular roads (lines) around the lake and scattered tourist and agricultural areas (points), and it must be said that organic cooperation is weak.

With a budget of approximately 8 billion yen (general account), of which over 1 billion yen is spent on social security, it is not realistic to wait for large-scale investment from outside. Therefore, I would like to propose reconstructing the Edo system philosophy with modern technology."Neo-Edo model"is.

Specific measures: Creating a spiral cycle

Specifically, we propose a "spiral transformation" in the following three areas. This is not just about building roads, but an attempt to synchronize the flow of people and money.

Particularly important is the perspective of "hybrid infrastructure for disaster prevention and tourism."

Just as Edo's "hirokoji" and "dotted banks" were places for people to relax in peacetime and also functioned as firebreaks and evacuation sites in times of emergency, Toyako Town should also be designed to serve as a "spiral promenade with spectacular views" that can serve as a "life-saving evacuation route to higher ground" in the event of an eruption of Mount Usu or flooding.

Budgetary measures solely for "preparing for a future disaster" are difficult to maintain in today's financially strained world. However, if "infrastructure that can be used every day and generates income" can "save lives in an emergency," then its maintenance costs can be justified as an investment. This is the ultimate resilience we should learn from the Edo period.