KAJIMA TREE — Kajima's Timber Tower Built from the Expo 2025 Grand Ring

KAJIMA TREE is the timber tower Kajima Corporation is building in the Urban GX Village at GREEN×EXPO 2027. Standing about 60m tall, it reuses timber from the Grand Ring, the symbol of Expo 2025 Osaka, Kansai, as its columns and beams, and is planned as the landmark “symbol tower” of the venue. Kajima’s Japanese tagline translates roughly as “a story of nature and people for tomorrow”, and the company presents the tower as a symbol of a new landscape for the cities of the future.

What to see

KAJIMA TREE is not an exhibition hall: the building itself is the attraction. The construction overview lists its use as a “memorial tower”, and whether visitors can go inside, or whether there will be a viewing deck or exhibits, has not been announced (as of October 2026).

• Timber that remembers the Expo: after about two years outdoors, the outward-facing surfaces of the Grand Ring timber turned grey, but a light shave reveals fresh wood. Some members still carry pavilion signage from Expo 2025, and Kajima’s designers say they want visitors to sense the memory of the forest and of the Expo in the wood.
• A tree-like form: the base braces itself like the roots of a large tree, and the tower rises in a gentle arc from the ground to the sky. The design team spent about two years refining the drawings.
• From ring to tower: between September 29 and October 2, 2026, Kajima’s official X account posted a four-part series, “HOW TO BE KAJIMA TREE?”, explaining each step from the Grand Ring to the tower.

Building and design

• Structure: timber plus seismic-control structure, about 60m tall. Designed by Kajima’s Architectural Design Division and built by its Yokohama branch, with construction running from June 2026 to February 2027.
• Kumiki seismic control system: tall, slender towers tend to bend as a whole under wind and earthquakes. KAJIMA TREE combines inter-column dampers (a vertical application of the system planned for Kajima’s new Tohoku branch building in Sendai, due in fiscal 2028) with boundary-beam dampers that connect the four corner cores, so the timber members absorb energy together.
• Reclaiming the timber: the Grand Ring used about 27,000 m³ of timber. Kajima bid in a public offering on “Myaku-Ichi!”, the Expo 2025 circular marketplace, and acquired about 3% of it. The wood was stored in Tatebayashi, Gunma Prefecture, strength-tested and repaired, then cleaned, machined, sanded and fitted with damper hardware at a processing plant. Column-and-beam units are pre-assembled on the ground for accuracy.
• Reuse below ground too: CO2-absorbing concrete paving blocks used at Expo 2025 and demolition material from Kajima’s former Yokohama branch building go into the foundation concrete.

About the exhibitor

Kajima is the recipient of Grand Ring timber from Expo 2025, according to the Expo Association’s Village page. The tower puts into practice the company’s “Kajima Environmental Vision 2050plus” (decarbonization, resource circulation and nature restoration). Kajima’s structural designer says the Kumiki system could eventually be applied to high-rise buildings.

Announcements so far

• October 1, 2024: the Expo Association announced its first eight Village exhibitors, including Kajima.
• October 29, 2025: at the 500-days-to-go press conference, Kajima presented the timber tower “KAJIMA TREE (tentative name)”.
• March 19, 2026: one year before opening, Kajima explained the Kumiki seismic system and the storage of the timber in Tatebayashi.
• May 13, 2026: a 1/100 model was unveiled at a timber-architecture fair at Tokyo Big Sight.
• June 1, 2026: groundbreaking ceremony at Kajima’s exhibition plot.
• September 14, 2026: main construction began and the assembly of reused-timber columns was shown to the press.
• October 1, 2026: the Expo Association’s official YouTube program “GREEN×EXPO DiRECT #23” featured the construction site.

Reactions on social media

Kajima’s official X account reported the start of assembly on September 18 and has been posting a step-by-step series since late September. On X, many posts point out the Expo 2025 pavilion signs still visible on the timber, and several people share photos of the tower growing taller from outside the venue. Some posts also mention it alongside Toho-Leo’s Yasashiku Naritai STUDIO as a legacy carried over from Expo 2025 (as of October 2026).

Before you go

• Location: Urban GX Village, near the Aizawa River according to Kajima’s venue map.
• Reservations: whether it will be covered by the same-day viewing reservation system has not been announced (as of October 2026). Entry to the tower and any viewing deck are also unannounced.
• Completion: planned for the end of February 2027, before the March 19, 2027 opening.
• Accessibility and children’s information: not yet announced.

Sources (all checked 2026-10-04):

• Expo Association: Village Exhibitions
• Kajima: KAJIMA TREE special site (Japanese)
• Kajima: FEATURES — designing the symbol of GREEN×EXPO 2027 (2026-07-06, Japanese)
• Kajima: FEATURES — the journey of the Grand Ring timber (1) (2026-07-06, Japanese)
• Kajima news: main construction of KAJIMA TREE begins (2026-09-15, Japanese)
• Kajima news: groundbreaking (2026-06-09, Japanese)
• Kajima news: 1/100 model unveiled (2026-05-13, Japanese)
• Kajima news: one year to go (2026-03-19, Japanese)
• Kajima news: exhibit announced at the 500-days press conference (2025-10-29, Japanese)
• Expo Association press release: first exhibitors announced (2024-10-01, Japanese)
• Expo Association: “GREEN×EXPO 2027 progress” (published by MAFF, June 2025; Village layout map, Japanese)
• Expo Association official YouTube: GREEN×EXPO DiRECT #23 (2026-10-01, Japanese)
• Kajima official X

Note: Exhibit details and highlights will be updated as official announcements are made.