What did the former arsenal sites become? Tokyo Dome, Morinomiya, Suzuka, and Hiratsuka

Published: October 31, 2026 / About 12 min read

The former arsenal sites did not all go the same way. At Suidobashi (Former Army Arsenal) in Tokyo the site became a ballpark and then a dome, at Morinomiya (Former Osaka Army Arsenal) in Osaka it split into a park, railway tracks, and town, at Suzuka (Former Naval Arsenal) in Mie it became a town lined with large private factories, and at Hiratsuka (Former Naval Powder Arsenal) in Kanagawa it became a factory for tires and rubber products. There are also cases that continued as military facilities: the City of Sagamihara explains that Sagamihara (US Army Depot) was used before the war by the former Imperial Japanese Army as the Sagami Army Arsenal and was requisitioned by the US military in 1949.

All four places share one thing: the factory occupied a wide, flat, continuous site, and after the factory left, that site moved on to its next use. If you compare the aerial photographs by era, the contents of each site change, but every location keeps lines that do not change position through the eras. Only a few locations, however, have photographs that show the factory itself, and whether it appears is decided by whether the year the factory left comes before or after the era of the photograph.

Eras that show the factory and eras that do not

When you read a former site in the photographs, the first thing to check is whether the location has a photograph from the time the factory was running. If you line up the oldest era that can be chosen at each location and the year the factory left, the locations where it appears and those where it does not separate clearly.

At Suidobashi, the move of the arsenal was completed in December 1936, and the oldest photograph is from around 1936-42. By the time the photograph was taken, the factory had already left. Morinomiya goes back to the photograph from around 1928, so the factory buildings appear. At Suzuka and Hiratsuka the oldest photograph is from 1961-69, and the photographs show the postwar factories.

Suidobashi: the open ground east of the garden becomes a ballpark

The arsenal at Suidobashi was an army weapons factory placed on the site of a feudal lord's residence from the Edo period; in 1927 it was decided to move it to Kokura in Kyushu, and the move was completed in December 1936. The photograph from around 1936-42 falls just after the move, and the area east of the woods of the garden shows up as bright ground with the buildings gone.

Facilities are added to that open ground era by era. The 1945-50 photograph shows an oval ballpark, the 1961-69 photograph shows a long, narrow oval track to its north, and in 1987-90 a white round roof sits where the oval used to be. In the company history, Korakuen Stadium opened on September 11, 1937, the Korakuen Velodrome on October 31, 1949, and Tokyo Dome on March 17, 1988.

Throughout this time, the outline of the woods of the garden has not changed shape in any photograph. Only the garden was kept out of the arsenal grounds, and facilities replaced one another in turn on the open east side; you can read this simply by stepping through the eras.

Morinomiya: a blacked-out photograph in between

In the photographs of Morinomiya, the same area has strikingly different colors from era to era. The later form of the site is touched on in the article that compares the redevelopment of former factory sites, so here the focus is on the differences between eras and the shape of the lots.

In the photograph from around 1928, a group of long, narrow buildings facing the same way stands east of the moat and woods of the castle. In the photograph from around 1936-42 that area is hidden under black paint, and how to read that black area is summed up in the article on the aerial photographs from around 1936-42.

In 1945-50 the black area is gone, and the remains of buildings that look as if they had lost their roofs stand in rows. In 1961-69 one site is divided into three strips: the park in the west, the bundles of railway tracks running north and south through the center, and the large dark buildings in the east, and this arrangement still holds in the color photograph from 1974-78. Morinomiya is the place where the photographs of a single location let you follow the site from the eras that show the factory to the era when it split into strips.

Suzuka: a city born for an arsenal

According to the records of Mie Prefecture, the City of Suzuka was born on December 1, 1942, and a naval arsenal was placed there on June 1, 1943, the next year; the city status seems to have been adopted in order to receive the arsenal. The arsenal was placed around Hiratacho Station, the terminus of the Kintetsu Suzuka Line. After the war, in November 1950, the city enacted the Factory Establishment Incentive Ordinance earlier than most of the country, and large spinning and chemical companies decided to move in.

In the 1961-69 photograph, rows of long, narrow buildings separated by right-angled roads and the large roofs of factories stand west of the center, and their lines are completely different in character from the narrow paths that wind through the paddies to the east. In 1974-78 the west fills with rows of houses and walled factory grounds, while the east is still paddy lots in 1979-83, and the north-south road that divides the two is in the same position in 1987-90 as well.

Hiratsuka: from a powder arsenal to a tire factory

According to the cultural properties page of the City of Hiratsuka, Nihon Kayaku Seizo was founded on December 5, 1905, and the factory site, which started at 380,000 tsubo, later grew to 420,000 tsubo. In 1919 the navy bought the company and made it the Naval Powder Arsenal, and after the war Yokohama Rubber received the site in a sale of government property.

In the 1961-69 photograph, long, narrow white factory roofs run in parallel southwest of the center, one white circle sits at their eastern end, and a straight north-south road divides the middle of the grounds. The rows of fruit trees to the northwest turn into brown bare ground in 1979-83, but the rows of roofs and the white circle stay in the same position.

The Hiratsuka site is a case where the grounds passed to the next company while remaining a factory. Because the use did not change, the arrangement of the roofs and the position of the white circle hardly change from 1961-69 to 1987-90. The field next door to the north changed instead, and the firmness of the lots on the former site and the changeability of the land around it form a pair in the same frame.

Years of events and the photograph eras

The years recorded in the sources consulted are set here beside the photograph eras of each location.

At Suidobashi, every event after the arsenal left falls within the span of a photograph era, so you can check in the photographs the order in which the facilities on the site were added one by one. At Suzuka and Hiratsuka, every event from the military period comes before the oldest photograph, and the photographs show only the form after private factories took over. Even among former arsenal sites, the stretch you can follow in the photographs differs this much.

The contents change, the lines that do not move remain

If you line up the four places, the ways the sites changed fall into two types. Suidobashi and Morinomiya are the type where the contents of the grounds were replaced entirely. At Suidobashi, facilities replaced one another on the east side while the garden stayed as a lot that did not move, and at Morinomiya one site was divided into strips of park, tracks, and buildings. Suzuka and Hiratsuka are the type where factory land passed to private owners while remaining factory land. Hiratsuka in particular is a case where even the contents of the grounds hardly move from 1961-69 to 1987-90.

In every type, the photographs keep lines that do not change position through the eras. The outline of the woods of the garden at Suidobashi, the bundles of tracks running north and south through the site at Morinomiya, the north-south road east of the factory grounds at Suzuka that divides the rows of houses from the paddies, and the rows of factory roofs and the white circle inside the grounds at Hiratsuka all stay in the same position between the two eras in the next table.

Where the arsenals were placed, seen through elevation

The height of the land where the arsenals were placed also differs from location to location. At Suidobashi the center is 4.4 m and the measuring point to the west is 3.1 m, and only the measuring point to the east is high at 16.4 m, a position where low land along the river reaches the edge of the plateau.

At Suzuka the measuring points in all directions fall between 22.4 m and 25.0 m, and at Hiratsuka between 7.2 m and 9.8 m. At both suburban places the difference between measuring points is less than 3 m, and the elevation figures also show that this was flat land where a wide site could be divided with continuous straight lines. The expected flooding of low land along rivers is collected from the published materials of each local government on the Hazard Map Portal Site of the Ministry of Land, Infrastructure, Transport and Tourism.

The surroundings of the former sites, seen through official land prices

The standard sites of the official land prices (Chika Koji) near Suidobashi, Suzuka, and Hiratsuka are all residential lots. The year the records begin differs by location, so the table sets side by side 2013 and 2026, the years all three share. The movement of the values near Morinomiya is covered in the article comparing the redevelopment of former factory sites mentioned earlier. None of the values is for the former site itself; each is for a residential lot a few hundred meters from the center.

Over the 13 years from 2013 to 2026, the price near Suidobashi became a little over 2.6 times as high. Over the same 13 years, the price near Suzuka rose by 800 yen and the price near Hiratsuka by 17,000 yen. The one place in the city center and the two suburban places move very differently over the same period.

Step through the eras to check

If you want to try reading a former site, the shortest way is to start with Morinomiya, which has eras that show the factory. If you switch back and forth between the photographs from around 1928 and around 1936-42, you can see the moment when the rows of buildings are hidden under a black area, and if you go on to 1945-50 and 1961-69, you can follow the order in which one site divides into three strips.

At Suidobashi, set the photograph from around 1936-42 beside the 1945-50 photograph and see where an oval appears on the open ground east of the garden. At Suzuka you can set 1979-83 beside 1987-90 and check that the road dividing houses from paddies does not move, and at Hiratsuka you can set 1961-69 beside 1987-90 and check that the rows of factory roofs do not move.

The prices in this article are actual examples at each point in time and do not reflect market prices after the article was written.