Tokyo Metropolitan Government Building Projection Mapping “City of Water: Edo Outer Moat”: The Sotobori Purification Project and Its Mid-2030s Water Plan

TOKYO Night & Light, the projection mapping shown on the east wall of the Tokyo Metropolitan Government No. 1 Building in Shinjuku, has been screening “City of Water: Edo Outer Moat” (水の都 江戸・外濠) since Saturday, November 1, 2025. It runs on Saturdays, Sundays and national holidays only, and each showing lasts about four minutes. Viewing from the Citizens’ Plaza (Tomin Hiroba) is free, and no reservation is required. The show is organized by the Tokyo Metropolitan Government and the Tokyo Projection Mapping Executive Committee, and was produced and created by HITOHATA, INC.

The work is linked to the Tokyo Metropolitan Government’s “Sotobori Purification Project” for the outer moat of former Edo Castle. On March 27, 2026, Tokyo published an implementation plan that will connect the outer moat with the Tamagawa Aqueduct and create a flow of water reaching Tokyo Bay. Based on announcements by Tokyo and HITOHATA, INC., this article sums up the show, the projection mapping held on the Edo Castle outer moat itself, and the purification plan.

*Disclosure: “City of Water: Edo Outer Moat,” the projection mapping at the Tokyo Metropolitan Government Building introduced in this article, was produced and created by HITOHATA, INC., an affiliate of HITOHATA ASSOCIATION, the general incorporated association that operates TOKYO ART SPHERE (About us).

What is “City of Water: Edo Outer Moat”? From Edo’s waterside to a future city

According to Tokyo’s announcement of October 22, 2025, the main program runs four minutes, and a 30-second promotional video was shown daily before the screenings. Tokyo presented the work as linking memories of Edo as a city of water with a vision of the future city, and invited viewers to enjoy a grand art experience, in step with the outer moat waterside regeneration project, in which the city and nature, tradition and innovation resonate with each other. The imagery moves from Edo’s waterfalls and waterside scenes to a future city and a water source where cherry blossoms are in full bloom, and the finale symbolizes the regeneration of Tokyo’s waterside continuing into the future.

HITOHATA, INC.’s event page says the work portrays waterfalls and waterside scenes from ukiyo-e prints, clear streams and flowers of the four seasons in a fantastical world. According to the official description, waterfalls and waterside scenes painted by Katsushika Hokusai and Utagawa Hiroshige come back to life in three dimensions, and indigo waves wrap the entire building; in the second half, a future city rendered in 3DCG appears. The show is a long run, and showtimes are announced on the official TOKYO Night & Light website. In March 2026, HITOHATA, INC. released an official record video of the work.

Title: TOKYO Night & Light “City of Water: Edo Outer Moat” (水の都 江戸・外濠)
Start: Saturday, November 1, 2025 (long run)
Days: Saturdays, Sundays and national holidays (showtimes on the official website)
Running time: About 4 minutes
Venue: East wall of the Tokyo Metropolitan Government No. 1 Building (viewed from the Citizens’ Plaza)
Admission: Free (no reservation required)
Organizers: Tokyo Metropolitan Government; Tokyo Projection Mapping Executive Committee
Producer: HITOHATA, INC.
Official website: https://tokyoprojectionmappingproject.jp/

The full TOKYO Night & Light schedule and lineup are covered in our TOKYO Night & Light guide. The screenings are certified by Guinness World Records for the “Largest architectural projection-mapped display (permanent),” as explained in our article on projection mapping Guinness World Records.

Projection mapping on the Edo Castle outer moat itself: 2024 and 2025

Tokyo has also held projection mapping that uses the outer moat itself as the screen.

The first edition ran from Thursday, May 30 to Sunday, June 2, 2024, from 7:30 p.m. to 9:00 p.m. Images were projected onto the embankment slope of the Ushigome Moat on the Edo Castle outer moat and viewed from Chiyoda City’s Sotobori Park; viewing was free and required no advance registration. According to Tokyo, the show expressed the image of an outer moat revived through better water quality, using Edo waterside scenery such as that depicted in Utagawa Hiroshige’s “One Hundred Famous Views of Edo.” About eight minutes of digital art were projected in total, including digital animation based on ukiyo-e that evoked Edo streets bustling with cherry blossom viewing and festivals and scenes of the four seasons, as well as nishikigoi carp and flowers. According to Tokyo, the event was chosen through UPGRADE with TOKYO (Bureau of Industrial and Labor Affairs), a pitch event in which startups propose solutions to metropolitan policy issues; the call was for content that lets people experience the outer moat waterside regeneration project and related history and culture, and the winner was HITOHATA, INC. According to the company’s history, it won the 32nd pitch event in October 2023, and in August 2024 Tokyo certified it, as a startup providing projection mapping that uses cultural tourism resources, as a company eligible for policy-purpose negotiated contracts (until March 31, 2027). How local governments commission projection mapping, and what it costs, is explained in our article on projection mapping project costs in local government calls for proposals.

The second edition, “Edo Castle Outer Moat Projection Mapping 2025,” was held from Thursday, November 20 to Sunday, November 23, 2025, from 5:00 p.m. to 8:30 p.m. It was projected onto the embankment slope of the Ushigome Moat in Ichigaya Tamachi 3-chome, Shinjuku City (a section of about 100 meters), and viewed from Chiyoda City’s Sotobori Park, about a 10-minute walk from both the west exit of JR Iidabashi Station and JR Ichigaya Station. According to Tokyo, an animation of about one minute introducing the project was followed by a story of light of about five minutes expressing hopes for the regeneration of the waterside. The projectors had twice the performance of the previous year’s, with brightness equivalent to 40,000 lumens. The event is also listed among HITOHATA, INC.’s events.

In November 2025, Tokyo presented the new show at the Metropolitan Government Building, the Edo Castle outer moat projection mapping and a study session for residents (November 15, at Iidabashi Grand Bloom) together as the “Sotobori Purification Project events.” The study session included a lecture on the Edo Castle outer moat by a Hosei University professor and a tour of the moat’s history and remains. As of November 9, 2026, we could not find any new announcement from Tokyo about a 2026 edition of the Edo Castle outer moat projection mapping.

The purification plan: linking the moat to the Tamagawa Aqueduct, with water flowing from the mid-2030s

The outer moat was dug as the outermost moat of Edo Castle between 1604 and 1636 through the so-called tenka-bushin, construction ordered by the shogunate and carried out by feudal lords. The eastern side has been filled in, but on the western side the moats remain between Iidabashi Station and Akasaka-mitsuke via Yotsuya Station, and they were designated a national historic site in 1956 (according to Tokyo). The purification covers three moats: the Ichigaya Moat, the Shin-mitsuke Moat and the Ushigome Moat.

According to an article on the Japan Science and Technology Agency (JST) Science Portal, the original outer moat made use of natural terrain such as valleys, and because the Tamagawa Aqueduct reached as far as around Yotsuya-mitsuke, it was built to take in aqueduct water, spring water and rainwater and pass them downstream. Today little water flows into the moats, so the water tends to stagnate, and in summer blue-green algae (aoko) can bloom and turn the surface murky green.

In its “Grand Design for Urban Development” of September 2017, Tokyo said it would systematically restore waterside spaces such as moats and ponds, and in September 2018 it set up a study group of related bureaus. It presented the “Sotobori Purification Project” in the “Future Tokyo” strategy of March 2021 and adopted a basic plan in May 2022. The project is now positioned under Strategy 19, “Greenery and Water,” of the “2050 Tokyo Strategy.” The implementation plan published on March 27, 2026, sets out the water conveyance facilities for the outer moat, the project period and the estimated cost.

According to the summary of the implementation plan, about 0.5 cubic meters of water per second is needed, to be secured from reclaimed sewage water and water from the Arakawa River (securing the water source is still being coordinated with the relevant organizations). The conveyance facilities will be built in four sections, A to D. The work includes improving and newly building more than 8 km of pipelines, building a new conveyance pump station, dredging and repairing about 10 km of conveyance channels, repairing about 2 km of the Tamagawa Aqueduct, building more than 2 km of new conveyance channels, and building an outlet into the outer moat designed with care for the historic site. Pipelines once used for industrial water will be converted into conveyance channels. The Bureau of Urban Development, the Bureau of Waterworks, the Bureau of Sewerage, the Bureau of Environment and the Bureau of Construction will share the roles.

Water conveyance is scheduled to begin in the mid-2030s. The estimated construction cost is 34 billion yen, factoring in rising prices; it excludes the cost of transferring pipelines between accounts, which is still under discussion. Maintenance is estimated to cost 240 million yen a year.

Editor’s view

Even if everything goes to plan, the water in the outer moat will become clean only after conveyance begins in the mid-2030s. It is a long-term project in which each section takes about nine to ten years, and Tokyo has explained that it holds the projection mapping to deepen residents’ understanding and draw interest to the outer moat. It can be seen as an attempt to show, ahead of time, a project whose finished form cannot yet be seen, through images of ukiyo-e waterside scenes and a future city.

The use of two different screens, the slope of the moat and the wall of the Metropolitan Government Building, also stands out. On the moat, the show uses the moat itself as its stage for just a few days; at the Metropolitan Government Building, it is screened every weekend. Seeing the historic site on location and a screening that reaches large audiences in Shinjuku convey the same project from different angles.

Frequently asked questions

When can I see “City of Water: Edo Outer Moat”?

It is screened on Saturdays, Sundays and national holidays on the east wall of the Tokyo Metropolitan Government No. 1 Building. Each showing lasts about four minutes; check the showtimes on the official TOKYO Night & Light website. Viewing from the Citizens’ Plaza is free and requires no reservation.

When will the water in the outer moat be cleaned up?

Under Tokyo’s implementation plan, water conveyance to the outer moat is scheduled to begin in the mid-2030s. The plan calls for about 0.5 cubic meters of water per second from reclaimed sewage water and Arakawa River water, though securing the water source is still being coordinated with the relevant organizations.

Where was the Edo Castle outer moat projection mapping shown?

In 2024 and 2025, it was projected onto the slope of the Ushigome Moat in Ichigaya Tamachi, Shinjuku City, and viewed from Chiyoda City’s Sotobori Park on the opposite bank. The park is about a 10-minute walk from both the west exit of JR Iidabashi Station and JR Ichigaya Station.

Outer moat waterside regeneration (Tokyo Metropolitan Government Bureau of Urban Development): https://www.toshiseibi.metro.tokyo.lg.jp/ryokuchi_keikan/mizujyunkan/mizube_saisei
*Information as of November 9, 2026. Please check the official websites for the latest information.

*Top image: TOKYO Night & Light “City of Water: Edo Outer Moat” (from a press release by HITOHATA, INC.)

*This article was compiled by the TOKYO ART SPHERE editorial team based on announcements by the Tokyo Metropolitan Government (May 24, 2024; October 22, 2025; March 27, 2026), the summary of the “Implementation Plan for Purifying the Outer Moat,” information on the HITOHATA, INC. website, and an article on the Japan Science and Technology Agency’s Science Portal (June 18, 2026).

Text: TOKYO ART SPHERE Editorial Team

A note from the publisher

*Disclosure: “City of Water: Edo Outer Moat,” the projection mapping at the Tokyo Metropolitan Government Building introduced in this article, was produced and created by HITOHATA, INC., an affiliate of HITOHATA ASSOCIATION, the general incorporated association that operates TOKYO ART SPHERE. The 2024 Edo Castle outer moat projection mapping was carried out based on the company’s proposal, which won Tokyo’s UPGRADE with TOKYO pitch event, and the 2025 event is also listed among the company’s events (About us).

The latest information on events produced by HITOHATA, INC. is available at HITOHATA, INC.’s event information. Inquiries about planning projection mapping and spatial staging are accepted through the company’s contact form.