The Second Seafort of Tokyo Bay, known as 第二海堡, is an artificial island located in the heart of Tokyo Bay, constructed over a span of 25 years during the mid-Meiji era. This remarkable feat of engineering, built using cutting-edge technology of the time, has become a cornerstone of modern marine civil engineering. After remaining off-limits for over a century, the island opened to the public in 2019, offering a unique extraordinary experience for visitors interested in historical military fortifications.

Often referred to as the Eastern Battleship Island, the Second Seafort was originally part of the Tokyo Bay Fortress aimed at protecting the capital and the Yokosuka Naval Base. Guided tours are now available, providing an opportunity to explore this intriguing site, which is rich with secrets and stories from its past. Visitors can embark on tours departing from nearby locations such as Yokosuka and Kisarazu, allowing them to discover not just the Seafort, but the many attractions in the surrounding area as well.