Yui Pond, Okinoshima

Yui Pond is a perfectly circular freshwater pond located on Okinoshima Island in the Oki Islands, Shimane Prefecture, Japan. This distinctive wetland area measures approximately 250 meters in diameter and forms part of the Oki Islands UNESCO Global Geopark. For many years, scientists debated the pond's origins, with theories ranging from volcanic crater remnants to meteorite impact sites. Recent geological studies have revealed that the pond was actually created by a large-scale landslide from surrounding cliffs, which formed a depression that subsequently filled with water.

The pond serves as a vital habitat for numerous species of birds, insects, butterflies, and dragonflies. The surrounding wet grassland ecosystem supports many precious plants and animals found throughout the region. Multicolored dragonflies are particularly abundant from early summer through autumn, making this an excellent destination for nature photography and birdwatching enthusiasts. The site is frequently used for environmental education workshops and eco-tours that highlight the island's unique biodiversity.

Visitors can explore the pond via a short walking trail that circles its perimeter, with two lookout decks positioned along the route for optimal viewing. A more elevated perspective is available from an additional lookout point located within 5 minutes walking distance, where observers can see Yui Pond from above with the sea and Dōzen Islands visible in the background. Note that parts of the path are currently closed due to damage and safety concerns.

The pond is situated in Okinoshima Town and can be reached by car from Saigō Port in approximately 40 minutes. Saigō Port serves as the main ferry terminal for Okinoshima Island, with regular ferry services connecting to mainland Shimane Prefecture. As the Oki Islands are a remote archipelago, visitors typically need to arrange car rental or taxi services once they arrive at the port, as public bus routes to the pond are limited. Admission to Yui Pond is free, though visitors should check current trail conditions before planning their visit due to ongoing maintenance work on certain sections of the walking paths.