Otaru Blue Cave: A Hokkaido Coastal Marvel

The Otaru Blue Cave, nestled along Hokkaido's scenic coastline, is a captivating natural attraction renowned for its vividly blue waters. This mesmerizing spectacle results from sunlight filtering through the crystal-clear seawater and reflecting off the unique geological features of the seabed. The cave's relatively shallow depth allows the longer wavelengths of blue light to bounce off the ocean floor, illuminating the cave's interior with an ethereal glow. Unlike the bright azure hue of Capri's Blue Cave, Otaru's volcanic rock seabed creates a deeper, more emerald-toned blue, offering a mysterious and serene atmosphere. The cave is located between Shioya and Otamoi, within the Niseko-Shakotan-Otaru Kaigan Quasi-National Park, known for its dramatic coastal landmarks. Visitors can explore the cave and its surroundings via various boat tours departing from Otaru Port, Shioya Port, or near the Otaru Canal. These tours often include views of other natural wonders, such as the Otamoi Coast, Red Rock (Akaiwa), and Todoiwa Rock, a winter resting spot for sea lions. Some tours also offer unique experiences like seagull feeding and mini fishing. Historically, the area around Otaru has been significant for trade and commerce, with the nearby Otaru Canal once serving as a vital transportation route. The west coast of Otaru, including the Shioya Coast where the Blue Cave is located, boasts a history dating back to the late Jomon period. While exploring the Blue Cave, visitors may also catch a glimpse of the ruins of Otamoi Amusement Park, a once-thriving resort area from the early Showa period. Though Ryugu-kaku, its grand dining hall, was lost to fire, remnants of the park add a layer of historical intrigue to the coastal scenery. Note that as of July 17, 2025, entering the cave is prohibited due to a wall collapse. Please confirm details of cruise routes with tour providers.