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. Most of the Expo venue is set to continue on as a park in the Disaster Prevention and Park District, while a part of the former venue falls within the district next door. In that neighbouring district, 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, 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 most of the Expo venue within the Disaster Prevention and Park District. A part of the former venue falls within the neighbouring Tourism and Vibrancy District, as described in the theme park section below.
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 “roughly 50 hectares” in the table above is the figure from the 2020 basic plan; the 650,000 square metres is the current plan’s figure on the city’s park-planning page. That 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.
In March 2024, the city drew up the outline of this “new park” concept. 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; its proposal is called KAMISEYA PARK (tentative name). 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. For this part of what was Expo ground, the document plans commercial facilities “with nature as the concept” attached to the theme park, rather than park land under the Disaster Prevention and Park District.
New transport
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.