Yano Aoyama Architecture Design Builds 80 m² Pavilion for Emperor

Japan has commissioned an 80-square-metre temporary pavilion, the Onodatesho, for the 76th National Tree Planting Festival, designed by Yano Aoyama Architecture Design for completion in 2026.

The pavilion follows a state tradition that dates to 1950: every year since then, Japan has commissioned a temporary piece of state architecture to host the National Tree Planting Festival. The event honours forest preservation but, as the architects note, it is "rarely publicized outside the archipelago."

Aoyama Eriko and Yano Toshihiro lead the design team. Nishikawa Masao photographed the project.

What is the Onodatesho?

The Onodatesho is the ceremonial pavilion at the centre of the festival, occupied by the Emperor and Empress during the event. It anchors the festivities, which celebrate tree planting and forest preservation across Japan.

The structure is temporary by design. Traditionally, workers dismantle the pavilion soon after the festivities end, leaving no permanent trace of the state commission.

How does the pavilion fit Japan's tree-planting tradition?

The National Tree Planting Festival, known in Japan as an annual rite of forest stewardship, has produced a new piece of ceremonial architecture every year since 1950. Each edition hosts the imperial couple and, once the ceremony closes, the pavilion comes down.

Key facts about the commission:

• Architects: Yano Aoyama Architecture Design
• Lead architects: Aoyama Eriko and Yano Toshihiro
• Area: 80 m²
• Year: 2026
• Edition: 76th National Tree Planting Festival
• Photographs: Nishikawa Masao

The 2026 pavilion continues a 76-year sequence of ephemeral state buildings, making it one of the longest-running temporary architecture programmes in the world — and one of the least documented internationally.

Why does a temporary imperial pavilion matter?

The programme's ephemerality inverts the usual logic of state architecture. Instead of monuments built to last, Japan commissions a structure whose demolition is scheduled from the outset. The architects describe the festival as "a significant ode to forest preservation," aligning the ritual of building and unbuilding with the cycle of planting and harvesting trees.

At 80 m², the pavilion is compact by the standards of state ceremonial architecture, sized for its single imperial function rather than permanence or public reuse.

Once the 76th festival concludes and the Onodatesho comes down, the next host region will commission its own pavilion, extending a tradition that has renewed itself annually for more than seven decades.