The narrow waterway that connects Japan's main islands and serves as a vital shortcut

Countries & Cities · Published 30 September 2026 Swipe more like this →

In short: Separating Honshu from Kyushu, the Kanmon Straits are a critical maritime artery for cargo ships traveling between the Sea of Japan and the Inland Sea. This narrow passage, once known to Westerners as the Straits of Van der Capellen, is a bustling hub of engineering, transit, and annual celebration.

The Kanmon Straits span 18 kilometres, acting as a vital shortcut for vessels moving between Korea, China, and major Japanese ports like Osaka and Tokyo. The waterway is defined by its varying width: it measures 2.2 kilometres at its eastern entrance and 3 kilometres at the western end, though it maintains a consistent 1 kilometre width for the majority of its length. The name itself is a portmanteau derived from its two anchor cities: Shimonoseki on the Honshu side and Moji, a ward of Kitakyushu, on the Kyushu side.

The region is a masterclass in infrastructure adaptation. Because the straits naturally silt up at a rate of 15 centimetres annually, constant dredging is required. This process has inadvertently provided a cost-effective foundation for major projects, including the New Kitakyushu Airport, which opened in March 2006. The area is home to approximately 1.3 million people, with about 1 million residing in Kitakyushu and 300,000 in Shimonoseki, though demographic definitions of the region vary.

Connectivity across the straits has evolved significantly over the last century. While traditional ferries remain a primary mode of transit, the passage is now dominated by a complex network of tunnels and bridges. The first railway tunnel opened in November 1942, followed by a highway tunnel in March 1958. By November 1973, the Kanmonkyo Bridge began carrying vehicles, and in March 1975, the Shinkansen tunnel was completed. Today, the straits serve as more than just a transit point; they are a site for cultural events like the annual August fireworks festival and a destination for aerial tourism, including helicopter tours and rare airship visits.

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