Rising approximately 70 meters above Osaka’s Expo ’70 Commemorative Park, the Tower of the Sun looms not merely as a relic of mid-century architecture, but as a monumental provocation. Built for the 1970 Japan World Exposition as the beating heart of Kenzo Tange’s massive, rationalist Big Roof—a space canopy stretching 292 meters long—artist Taro Okamoto’s creation ruptured the fair’s techno-optimistic narrative.
Where the exposition celebrated hyper-industrial efficiency and orderly progress under the banner of “Progress and Harmony for Mankind,” Okamoto erected an ancient, mythic totem that pierced straight through Tange’s steel framework, demanding an encounter with the chaotic, spiritual roots of human vitality.
The Four Mythic Canvas Faces of Time
Okamoto envisioned the tower as a cosmic nexus—a central pillar for matsuri (festivals) and a vessel unifying past, present, and future. This temporal alchemy is expressed through its iconic, distinct visages.
The Golden Mask crowns the summit at 10.6 meters in diameter. Crafted from special gold polyvinyl chloride films bonded to stainless steel plates, its 2-meter-wide eyeballs glint in the sky, gazing toward an unwritten future.
On the tower’s chest sits the Face of the Sun, a 12-meter fiberglass-reinforced plastic (FRP) relief coated in sprayed concrete and resin, capturing the raw, immediate presence of the living present.
Around the back lies the Black Sun, an 8-meter disc inlaid with dark Shigaraki ceramic tiles, representing the quiet shadow of memory and the deep past.
The Missing Fourth Face
During Expo ’70, a mysterious fourth face—the Underground Sun—was situated in the subterranean realm of the Theme Pavilion’s Harmony Plaza. Measuring roughly 3 meters high and 11 meters long, it anchored the subterranean exhibition on the “Mystery of Life.”
Following the dismantling of the Expo, this vast sculpture vanished from public records and storage facilities, leaving behind an unsolved art historical mystery that only deepens the tower’s folkloric aura.
Engineering an Avant-Garde Monument
Translating Okamoto’s organic, tapering form into a resilient structure required a hybrid approach to structural engineering. The tower incorporates three distinct structural systems from its base to its summit:
The outer skin sparkles with vibrant glass mosaic tiles produced in Italy—striking Red Streaks of Lightning across the front torso and Green Solar Corona Waves along the back. Constructed between January 1969 and March 1970 at a cost of approximately 630 million yen, the structure absorbed shotcrete technique innovations to save structural weight while preserving its fluid, sculpted silhouette.
The Sacred Interior: The Tree of Life
To experience the tower during the 1970 exposition was to participate in an epic physical ascent through deep biological time. Visitors entered the subterranean level, moving from primitive, primordial chaos upward through the hollow trunk of the tower along a central spine known as the Tree of Life (Seimei no Ki).
Anchor-bolted within the hollow tower interior stands this 41-meter-high steel trunk, sporting vibrant branches laden with 292 sculpted models of living organisms. The installation traces the evolutionary journey from microscopic amoebae through prehistoric reptiles to the arrival of humanity.
After Expo ’70 closed, the subterranean halls were backfilled and Tange’s Big Roof was disassembled between 1977 and 1978. The interior of the Tower of the Sun remained sealed in dark silence for nearly half a century before its eventual restoration—preserving Taro Okamoto’s radical vision as an enduring monument to human vitality.