A Launch Pad Built in the Sea
The Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform (旧佐世保海軍工廠川棚魚雷遠距離発射場射場) is an artificial island built in 1918 off the west shore of Katashima in Kawatana, Nagasaki Prefecture, to launch test torpedoes, and it was registered as a Registered Tangible Cultural Property of Japan on August 15, 2024. It sits about 50 meters out in the water, a concrete rectangle 11.52 meters east to west and 24.04 meters north to south. The official record gives its area as 276 square meters, which matches.
This is where torpedoes left for Omura Bay. A channel 3 meters wide is cut into the island's southern end, and two brick structures once straddled it: a single-story house on the west side and a three-story tower on the east. Torpedoes are thought to have been released into the sea through that slot.
Only the eastern tower still stands, with a footprint of 6.5 square meters. The western house has collapsed to a fragment of side wall. The two were once linked by a walkway running from the tower's second floor to the house's roof.
Why It Was Registered
Japan's Agency for Cultural Affairs describes the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform as a facility built solely for torpedo test firing, and a military remain rare anywhere in the country. Few sites preserve the launch slot, the tower and the rail bed together.
The engineering matters too. The island's base is built by stacking precast concrete blocks, a technique first used for the old Akasaki quay wall in Sasebo. According to the approved plan of 1917, each block was 3 shaku (a traditional unit of length) high on a base of 4 by 6 shaku, mixed with 3 by 6 and 2 by 6 shaku pieces, and stacked 13 courses deep at the deepest point. Kawatana's preservation plan treats it as an early experiment in moving a quay-wall method out into open water.
More than a century on, the foundation has barely shifted and the concrete is in good shape. Waves have chipped the upper surface, but the crane footing and the tracks that carried torpedoes out to the launch point are still clear.
Reading the Tower
The eastern tower rewards a close look. A 50-centimeter square pier rises at each corner through all three stories, pulling the eye upward; each pier head carries three ribs, and a doubled horizontal eave caps the whole. For a navy utility building the design is surprisingly modern, and the town notes echoes of it elsewhere in the Sasebo Naval District.
A steel lookout once sat on the roof. The approved plan puts its top at 49.5 shaku, about 15 meters above the base. The lookout is gone, but its steel footings remain on the roof slab.
At the end of the war the tower's floors, stairs and window openings were destroyed, which is why it now reads as a hollow shaft of empty frames. Experts have warned that the damaged second-floor slab of the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform could collapse, and repairing and bracing it is among the town's first priorities.
What You Can See, and From Where
Signs close the entrance to the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform, so you cannot cross to the island. Viewing is from shore. Stand near the landward end of the jetty and the arches, the island and the tower line up in a single sightline, tracing the exact route torpedoes traveled.
The tower's southeast face is the angle the national database uses for its main photograph. Morning light from the east brings out the corner piers and the stepped eaves.
Directions to Katashima Park and general visiting information are gathered on the page for the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range as a whole.
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Q&A
- Can you walk out to the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform?
- No. The entrance is signposted as closed, and the island can only be viewed from shore. Experts have flagged the damaged second-floor slab of the tower as a collapse risk.
- When was the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform built?
- In 1918, when the long-range torpedo range was built on Katashima. It was constructed as an artificial island about 50 meters offshore.
- What is the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform made of?
- The island is built from stacked precast concrete blocks. The surviving tower combines brick walls with reinforced concrete floors and roof.
- What stood on the roof of the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform?
- A steel lookout, rising to about 15 meters according to the approved plan. The lookout is gone, but its steel footings remain on the roof.
- When did the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform become a Registered Tangible Cultural Property?
- On August 15, 2024, together with the jetty and three other structures of the range, five in all.
Basic Information
| Name | Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform |
|---|---|
| Location | Katashima offshore area, Mitsukoshi-go, Kawatana-cho, Higashisonogi-gun, Nagasaki Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2024/8/15 (Reiwa 6) |
| Quantity | 1 structure |
| Dimensions | Launch platform of concrete, area 276 square meters, with launch tower (brick and reinforced concrete, 3 stories, building area 6.5 square meters) |
| Owner | Kawatana Town |
| Public Access | Inside Katashima Park; exterior viewable from shore, free. No access to the platform itself |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00015106
- Kawatana Town: Preservation and Use Plan for the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range (Japanese)
- https://www.kawatana.jp/cat03/c3-03/post_732/index.html
- Kawatana Town Tourism Guide: Torpedo Launch Test Site (Japanese)
- https://www.kawatana.jp/kankou/2010/12/post-24.html
- Cultural Heritage Online: Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range Firing Platform (Japanese)
- https://bunka.nii.ac.jp/heritages/detail/541274
Last verified: 2026.09.25
