Lake Inawashiro is Japan's fourth-largest lake, located in central Fukushima Prefecture within Bandai-Asahi National Park. Known locally as "Heavenly Mirror Lake" (Tenkyōko), the lake earned this poetic name from its crystal-clear surface that reflects the towering form of Mount Bandai and the sky above. The lake was formed between 30,000 and 40,000 years ago when volcanic eruptions from Mount Bandai and Mount Nekoma created a tectonic depression dammed by pyroclastic flows. Archaeological evidence suggests human habitation around the lake dates back approximately 12,000 years, with artifacts from the Jomon period discovered both onshore and in the lake bed.
Lake Inawashiro covers a surface area of 104 square kilometers with a circumference of 63 kilometers and reaches depths of up to 94 meters. The lake sits at an altitude of 514 meters and possesses distinctive acidic water with a pH of approximately 5.0 due to sulfuric inflows from hot springs and mineral deposits in the drainage basin. This acidic composition contributes to the lake's exceptional clarity. The water has been vital to the region's agriculture since ancient times, with irrigation channels constructed during the Edo period in the 17th century and expanded in 1882 to support rice cultivation across the Aizu and Koriyama basins.
Visitors can experience the lake's seasonal transformations throughout the year. During winter and early spring, migrating swans gather around the lakeshore, with approximately 3,000 swans arriving annually. The winter months also bring the unique "shibuki-gori" phenomenon, where strong western winds splash lake water onto shoreline trees, instantly freezing to create natural ice sculptures.
Summer offers swimming, fishing, boardsailing, and water skiing opportunities, particularly around the northern Nagahama shore, with camping facilities available for extended stays. Spring features cherry blossoms at notable sites like the Oshika Zakura elk cherry tree at Iwahashi Shrine, recognized as one of the Aizu district's five most famous cherry trees. Autumn transforms the surrounding mountains into displays of vibrant foliage reflected in the lake's mirror-like surface.
The lake area provides access to several cultural attractions. The Hideyo Noguchi Memorial Museum commemorates the renowned Japanese scientist who researched yellow fever and whose portrait appears on the 1,000-yen note. The Morohashi Museum of Modern Art houses the only permanent Salvador Dalí exhibition in Asia. Nearby attractions include the rainbow-hued Goshikinuma ponds and the Inawashiro Herb Garden, featuring 500 varieties of herbs and flowers across 100,000 square meters. Sightseeing boat cruises operate on the lake, with 35-minute tours departing hourly.
From Tokyo, take the Tohoku Shinkansen to Koriyama Station (approximately 90 minutes), then transfer to the Ban-Etsu West Line rapid train to Inawashiro Station (40 minutes). The total journey takes under three hours. Bus and taxi services connect the station to lakeside areas, with some hotels offering shuttle services from Koriyama Station. Rental cars provide the most flexibility for exploring the broader region. The lake itself has no admission fee, though individual attractions and activity rentals carry separate charges.
