The former Kamiseya Communication Facility, in Yokohama’s Seya and Asahi wards, does not stop mattering once GREEN×EXPO 2027 closes on 26 September 2027. The City of Yokohama set out a basic land use plan for the roughly 242-hectare site back in March 2020, dividing it into four districts. The Expo venue itself is set to continue on as a park. In the district next door, a group of eleven private companies led by Mitsubishi Estate is planning a theme park.
GREEN×EXPO 2027 runs from 19 March to 26 September 2027. What follows is drawn from official material published by the City of Yokohama and the GREEN×EXPO Association (formally the 2027 International Horticultural Expo Association, a public interest incorporated association), as far as we could confirm it in September 2026.
The former Kamiseya site’s four districts
The site was requisitioned by the US military in 1945 and fully returned to Japan on 30 June 2015. For the roughly 70 years in between, use of the land was restricted, though landowners continued farming much of it. About 45% is national land, another 45% is privately owned, and the remaining 10% belongs to the city.
Yokohama’s basic plan splits the site into four districts: Agricultural Promotion, Tourism and Vibrancy, Logistics, and Disaster Prevention and Park. The last was originally named the “Park and Disaster Prevention Zone” when the plan was adopted, and was renamed “Disaster Prevention and Park District” in the 2023 design note that followed up on the basic plan.
| District | Purpose | Area (as of 2020) |
|---|---|---|
| Agricultural Promotion | A model for profitable, high-value urban agriculture, including harvest experiences, direct-sales outlets and research with universities | Roughly 50 hectares |
| Tourism and Vibrancy | An area built around a theme park, drawing visitors from Japan and abroad | Roughly 125 hectares |
| Logistics | An efficient domestic logistics base, using its access to the Tomei Expressway and the Hodogaya Bypass | Roughly 15 hectares |
| Disaster Prevention and Park | A park carrying forward the Expo’s legacy, plus a wide-area disaster response base | Roughly 50 hectares |
City documents place the Expo venue within the Disaster Prevention and Park District.
The venue becomes a new city-run park
According to the city, the “(Tentative Name) Former Kamiseya Communication Facility Park,” within the Disaster Prevention and Park District, covers about 650,000 square metres across Seya-cho in Seya Ward and Kamikawai-cho in Asahi Ward. The city’s park-planning page states that this park will serve as the GREEN×EXPO 2027 venue, and that after the Expo it will keep developing around the themes of “environment” and “disaster prevention,” carrying forward the Expo’s ideas.
The outline of the concept was drawn up in March 2024. Basic infrastructure and planting are being put in place ahead of GREEN×EXPO 2027 opening. In March 2025, Yokohama revised its earthquake disaster prevention strategy to designate the former Kamiseya site as a base for large-scale disasters. The city says the park is planned to serve as a base camp for military, police and fire response teams arriving from across the country, and as a base for receiving and distributing relief supplies.
The theme park planned for the Tourism and Vibrancy District
The city opened a call for developers for the Tourism and Vibrancy District in February 2023 and selected Mitsubishi Estate Co., Ltd. that September. Mitsubishi Estate is the lead of an eleven-company group that also includes Sotetsu Holdings, Tokyu Fudosan, Tokyu, and Sumitomo Corporation, among others.
According to the planning-stage environmental scoping document Mitsubishi Estate submitted to the city in March 2026, the project area spans roughly 70.65 hectares across Kamikawai-cho and Seya-cho. It is organised around a roughly 51-hectare “Theme Park Zone,” alongside a station-front zone around the planned “(Tentative Name) Kamiseya Terminal,” a park-adjacent zone, and a zone west of the Kanjo 4 ring road. The stated aim is a next-generation theme park built on Japanese content and technology, explicitly carrying forward the ideas of GREEN×EXPO 2027. Opening is targeted for the early 2030s, with an operating period of more than 50 years; construction is planned to start in or after 2028, after the Expo has closed. The operator expects 12 million visitors a year at opening, rising in stages toward more than 15 million. The scoping document was open for public inspection at the city from 15 to 30 April 2026.
Within that area, the roughly 6.55-hectare “Park-Adjacent Zone” is described in the document as land that was part of the GREEN×EXPO 2027 venue. So part of what was Expo ground is set to become commercial space attached to the theme park, rather than park land under the Disaster Prevention and Park District.
New transport, and what the Association has not said
The 2020 basic plan called for a medium-capacity rail-type system, such as an LRT, running from Seya Station. The city’s current “New Transit Development Project” page, last updated in August 2026, instead describes introducing a new transport service between Seya and the former Kamiseya site together with expanded bus routes on surrounding roads. Mitsubishi Estate’s scoping document is more specific: it describes connecting the planned Kamiseya Terminal to Seya Station on the Sotetsu Main Line by bus, using self-driving, platooning technology. Urban planning procedures have reached the stage of an operator briefing in January 2026, a city draft-plan briefing in May, and a public hearing in July. The original rail-type scheme, the tentatively named Kamiseya Line urban rapid transit project, was formally dropped: the city’s environmental impact assessment register records a notice of project discontinuation dated 27 March 2024, published on 15 April 2024.
The GREEN×EXPO Association’s own site does not appear to have a page addressing how the venue will be used after closing. Its September 2026 press release does use the word “legacy,” but that release concerns a sustainability report required under International Association of Horticultural Producers (AIPH) rules, a different subject from what happens to the land itself. Decisions about the site’s future use rest with the City of Yokohama.
Our take
Osaka’s Expo ‘70 Commemorative Park, the Tsukuba Expo Centre, and the Aichi Expo Memorial Park each carried the whole of their former venue forward as a single park or memorial facility. Kamiseya looks set to take a different shape. The Expo venue, within the Disaster Prevention and Park District, becomes a park, but that is only 65 of the site’s 242 hectares. The Tourism and Vibrancy District next door is not being developed by the city at all, but by Mitsubishi Estate’s eleven-company group, as a theme park. Part of the actual Expo venue, the Park-Adjacent Zone, is even folded into that theme park’s commercial space rather than staying park land. Unlike Aichi, where the whole venue became one park, or Osaka’s 1990 flower expo, where the main pavilion itself continued on as a botanical garden, Kamiseya looks headed toward a public disaster-prevention park sitting right next to a privately run theme park, on the same former site.