The Floating Islands of Ōnuma: A Mystical Pond Where Islands Drift Across the Water
Hidden deep within the forested hills of Asahi Town in Yamagata Prefecture lies one of Japan's most enigmatic natural wonders: Ōnuma no Ukishima, the Floating Islands of Ōnuma. On the still, mirror-like surface of a small mountain pond, more than thirty islands of varying sizes drift silently across the water. Some are no larger than a stepping stone, while others stretch several meters across. They move on their own, without regard for the wind, sometimes pausing along the shore, sometimes circling the center of the pond, then quietly resuming their journey. For over 1,300 years, this scene has been regarded as sacred, and in 1925 it was officially designated a National Place of Scenic Beauty by the Japanese government.
A Sacred Pond with Over Thirteen Centuries of History
The story of Ōnuma reaches back to the late 7th century. According to tradition, the pond was discovered in 681 CE by En no Ozunu, the legendary mountain ascetic who is regarded as the founder of Shugendō, Japan's syncretic mountain-worship tradition. His disciple Kakudō later established a small shrine on the site, which would in time become Ukishima Inari Shrine, one of the oldest shrines in Yamagata.
In 739, the renowned Buddhist monk Gyōki is said to have visited Ōnuma and given names to sixty-six of the floating islands, each corresponding to one of the historical provinces of Japan. From that time onward, the slow drifting of the islands was treated as a form of divination: their movements were read as omens of fortune, harvest, and warfare. The shrine drew the devotion of warlords across the centuries, including the Ōe clan, the Mogami clan, and ultimately the Tokugawa shogunate, which placed the entire village under its direct protection during the Edo period and granted the shrine the rare privilege of bearing the three-leaf hollyhock crest.
Why It Was Designated a National Place of Scenic Beauty
Ōnuma no Ukishima was registered as a National Place of Scenic Beauty (Meishō) on October 8, 1925, under Japan's Law for the Preservation of Historical Sites, Places of Scenic Beauty and Natural Monuments. The Agency for Cultural Affairs describes the site as one of the most celebrated floating-island ponds in the entire country, noting that its islands form when the dense, tangled rhizomes and roots of reeds along the pond's edge break free and rise to the surface as buoyant masses. Wisteria, azaleas, and irises sometimes take root and bloom on these drifting clumps.
What sets Ōnuma apart from other floating-island sites in Japan is the autonomous motion of the islands themselves. Even on perfectly windless days, they shift slowly in different directions, occasionally pausing and then beginning to move again, a phenomenon described by the official designation as "extraordinary beyond words." The site was already famous in the Edo period thanks to the travel writer Tachibana Nankei (1754–1805), who described it in his celebrated travelogue Tōyūki (Records of Eastern Travels), bringing the pond to the attention of literati and poets across Japan.
Highlights and What to See
The Drifting Islands
Visitors come above all to witness the islands themselves. The best viewing times are early morning and evening from spring through early autumn, when the difference between day and night temperatures sets the islands gently in motion. Their diameters range from roughly 30 centimeters to over three meters, and on a calm day a single island may travel several meters across the pond's surface. The phenomenon is so subtle and unhurried that some visitors stand for an hour at the water's edge before noticing that an island has shifted entirely from where it began.
The Walking Path and Surrounding Forest
A well-maintained walking trail loops the entire perimeter of the pond, taking visitors through a hushed forest of ancient trees. Roughly three hundred species of plants grow naturally within the precincts, and the seasonal changes are striking, from new green and azaleas in spring to dense summer canopies, vivid autumn colors, and winter snow. The pond is also home to colonies of crimson koi that gather near the wooden footbridges, making for a particularly photogenic scene.
Ukishima Inari Shrine
The entire pond lies within the precincts of Ukishima Inari Shrine, regarded as one of Yamagata Prefecture's oldest shrines. Originally venerated as a guardian of family safety, healing, good fortune, and martial valor, the shrine today welcomes visitors who pray for safe travel, traffic safety, and success in study. The Kasasagi-bashi, or Magpie Bridge, is one of its iconic features and a popular photo spot.
The Annual Island Festival
The most distinctive event of the year is the Shima Matsuri, or Island Festival, held on the third Sunday of July. During the ceremony, a new island is cut from the reed beds at the pond's edge and named after the historical province lying in that year's auspicious direction. Accompanied by the rare music of Ukishima Gagaku, parishioners then float the newborn island toward the center of the pond as a prayer for the prosperity and good health of the community.
Around the Area
Asahi Town, set in the foothills of the Asahi Mountains, offers a quiet rural landscape rich in heritage and seasonal beauty. Within a short drive of the pond, visitors can explore the Sawatainara Rice Terraces (Sawatainara no Tanada), one of Japan's officially recognized "100 Best Rice Terraces," and stop at the towering ancient cedar known as the Matsubo no Ōsugi. The Asahi Shizenkan resort offers hot springs, lodging, and skiing in winter, while orchards in the area are famous for their apples, including the distinctive bagless varieties pioneered locally. Direct-sales markets such as the Oishī Dewa Sanchoku Ichiba make a pleasant stop for fresh seasonal produce, and the small candle workshop Hachimitsu no Mori Candle offers handmade beeswax candle experiences.
- 📍 Plan Your Visit to Yamagata
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Q&A
- When is the best time of year to see the islands actually moving?
- From spring through early autumn, especially in the early morning and late afternoon. The islands move most visibly when the temperature differs significantly between day and night. The site is closed during winter due to heavy snowfall.
- How large are the floating islands, and how many are there?
- More than thirty islands drift on the pond, with some sources counting as many as fifty to sixty. Their diameters range from about 30 centimeters to over three meters, and a few are large enough to support flowering plants such as wisteria, azaleas, and irises.
- How do the islands actually move without wind?
- The islands are formed from densely intertwined reed rhizomes and roots that have separated from the pond's edge. Subtle convection currents created by temperature differences in the water are believed to nudge the buoyant masses across the surface, producing motion that appears almost willful.
- Is there an admission fee, and how long does a visit take?
- There is no admission fee. Walking the loop trail around the pond takes roughly thirty to forty-five minutes at an unhurried pace, though visitors who wish to watch the islands move and explore the shrine should plan for one to two hours.
- Can I attend the Shima Matsuri Festival?
- Yes. The festival is open to the public and held on the third Sunday of July each year. It is a rare opportunity to see traditional Ukishima Gagaku court music performed and to witness the ritual creation of a new island.
Basic Information
| Name | Ōnuma no Ukishima (The Floating Islands of Ōnuma) |
|---|---|
| Designation | National Place of Scenic Beauty (Meishō), designated October 8, 1925 |
| Location | 984 Ōaza Ōnuma Aza Hira, Asahi Town, Nishimurayama District, Yamagata Prefecture 990-1305 |
| Pond Area | Approximately 30,600 m² |
| Owner | Ukishima Inari Shrine |
| Discovery | Said to have been discovered in 681 CE by the mountain ascetic En no Ozunu |
| Admission | Free |
| Closures | Closed in winter from snowfall until thaw |
| Parking | Available on site |
| Inquiries | Asahi Town Tourism Association (TEL: 0237-67-2134) |
| Annual Event | Shima Matsuri (Island Festival), held on the third Sunday of July |
References
- Cultural Heritage Online (Agency for Cultural Affairs) — Ōnuma no Ukishima
- https://bunka.nii.ac.jp/heritages/detail/171455
- Asahi Town Official Website — Ōnuma no Ukishima (National Designated Place of Scenic Beauty)
- https://www.town.asahi.yamagata.jp/portal/soshikinogoannai/kyoikubunkaka/shogaigakushugakari/4_1/2397.html
- Yamagata Prefecture Official Tourism Site — Ōnuma no Ukishima & Ukishima Inari Shrine
- https://yamagatakanko.com/attractions/detail_9467.html
- Visit Yamagata — Ōnuma no Ukishima
- https://www.visityamagata.jp/spot-asahi-ukishima/
- Asahi Town News — The Birth of "Echigo no Shima" at the Shima Matsuri
- https://www.town.asahi.yamagata.jp/portal/soshikinogoannai/seisakusuishinka/kouhoubrandgakari/6/9/2349.html
- Yamagata Prefecture Cultural Property Database — Ōnuma no Ukishima
- https://www.pref.yamagata.jp/cgi-bin/yamagata-takara/?m=detail&id=1146
Last verified: 2026.05.06