Osaka Expo '70 and the Forgotten Plan to Build a Plaza With a Brain

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An English translation of the plan for Festival Plaza, the central attraction of the Osaka World Expo 1970, has been published for the first time.

Largely overlooked by historians, the report, nicknamed "The Red Book," reveals an ambitious collaboration between computer scientists, musicians, science fiction writers, and architects. It offers a glimpse into a period when Japan was exploring how technology, art, and entertainment could be integrated to improve society.

The translation appears in The Red Book: Architecture, Collaboration and the Osaka Expo '70, published by Marcela Aragüez, Assistant Professor and Director of the Master in Architecture program at IE University. Aragüez believes the plan's ideas about interdisciplinary collaboration, innovation, and public space design remain relevant today.

Asia's First World Expo

Held in Osaka in 1970, Expo '70 was a showcase of Japan's postwar recovery presented to an international audience.

The event attracted more than 64 million visitors, equivalent to more than half of Japan's population at the time, and held the record for the most-visited World Expo for almost 40 years.

At the center of the Expo stood Festival Plaza, a vast covered venue where Emperor Showa officially opened the event and where many of the exposition's major performances and events were held.

Its enormous Big Roof, one of the world's largest space-frame structures at the time, demonstrated Japan's engineering capabilities while creating a futuristic public space where millions of visitors could gather.

Rising through the roof at the center of the plaza was Taro Okamoto's Tower of the Sun, which became the defining symbol of the Expo.

Although Kenzo Tange and Arata Isozaki are the figures most closely associated with Festival Plaza, Aragüez's book reveals that the project was shaped by more than 20 contributors from diverse fields.

Creating a Responsive Environment

One of the most ambitious ideas outlined in the Festival Plaza plan was the creation of a "responsive environment"—a space that would respond to visitors' movements and behavior rather than simply host them.

Today, interactive environments are common at events and exhibitions, but in 1970 the concept was still experimental. The designers envisioned a plaza that could sense crowds and respond in real time through light, sound, water, and movement.

The report described robots, computer-controlled lighting and water systems, and a central "artificial brain" that would coordinate the entire environment based on visitor activity.

Three robots were proposed, although only two were built, and the final versions differed significantly from the original designs. A computer system intended to function as the plaza's "artificial brain" was also developed, but technical problems prevented it from reliably communicating with the devices it was meant to control.

As a result, many elements, including seating platforms and robots, had to be operated manually.

Nevertheless, Aragüez argues that the ideas behind the project represented an early attempt at concepts that would later become familiar in responsive technology and interactive design.

"The devices that were implemented were, in a way, an embryonic version of what responsive environments would become," she said.

Freedom on a Leash

Another aspect of Festival Plaza that Aragüez finds particularly interesting is the balance between freedom and control.

The plaza was designed as an open space where visitors could move freely rather than follow a fixed performance schedule. To achieve this, the planners looked to examples of crowd movement, including Japanese summer festivals, to understand how large groups could be organized without making people feel restricted.

The report examined how people moved through traditional matsuri, mapping activity patterns on city streets and using those observations to inform the plaza's design.

Aragüez notes that these festivals, while appearing spontaneous, are carefully organized. Their sense of freedom comes not from a lack of structure but from structures that subtly guide movement. Festival Plaza followed a similar principle: visitor behavior was managed, but in a way that remained largely invisible.

"There is always some kind of management," she said, whether through physical design that encourages certain movements or through systems that monitor activity.

This balance between guidance and freedom continues to shape public spaces today. Shopping malls, train stations, stadium entrances, and other large public areas are designed to make movement feel natural while quietly influencing where people go.

Even in Japan's complex railway systems, there is no one instructing passengers at every turn. Instead, architecture, signage, and design guide people through the environment.

Giving Credit Where It's Due

Another revelation in The Red Book is the role of architect Atsushi Ueda, whom Aragüez believes has been overshadowed in historical accounts of Festival Plaza.

Ueda, who is still alive and lists Festival Plaza among his achievements on his personal website, worked with Isozaki during the later stages of the plaza's design. However, his contribution has often been absorbed into Isozaki's broader reputation.

"There is no hierarchy as to whether Isozaki or Ueda are more or less important," Aragüez said, while acknowledging Isozaki's significant influence on Japanese architecture before and after Expo '70.

Major architectural projects are rarely the work of a single individual. Similar questions about recognition and authorship persist across fields such as architecture, design, and film, where credit often accrues disproportionately to the most famous figure rather than to the wider team.

A Vision That Endured

While the technology of 1970 could not fully realize the ambitions outlined in the Red Book, Aragüez argues that the effort itself helped lay the groundwork for later developments in responsive design.

The Expo captured a moment of technological optimism, offering millions of visitors a glimpse of how innovation could transform everyday life. It arrived at a time when color television was entering homes across Japan and computers, robots, and space exploration were reshaping the public imagination.

More than 50 years later, as artificial intelligence and other emerging technologies continue to reshape society, Expo '70 remains a reminder that innovation begins with imagination—and that technology advances most through cross-disciplinary collaboration.

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Author: Daniel Manning

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