Oyunuma Observatory

Oyunuma Observatory offers visitors a dramatic vantage point overlooking one of Noboribetsu's most active geothermal features. Located in the Noboribetsu Onsen area of Hokkaido, Japan, this viewing platform provides safe access to observe Oyunuma, a natural sulfurous pond that maintains temperatures between 40-50°C year-round. The milky gray-blue waters stretch approximately 50 meters in diameter and reach depths of 2 meters, constantly bubbling with volcanic activity from below.

The observatory sits within Shikotsu-Toya National Park, an area recognized for its volcanic landscape and concentration of hot spring resorts. Noboribetsu itself has been a renowned onsen destination since the Edo period, though modern development of the area accelerated after 1858 when local entrepreneur Takimoto Kinjiro began promoting the therapeutic waters. The Oyunuma pond and surrounding geothermal features have served as both natural attractions and sources for the region's famous hot spring baths.

Visitors approach the observatory via a well-maintained walking path through forested terrain, with the entire route taking approximately 10 minutes from the Oyunuma parking area. The platform itself provides unobstructed views of the steaming pond and surrounding volcanic terrain, with informational signage explaining the geological processes at work.

A nearby footbath called Oyunuma River Natural Footbath allows visitors to experience the geothermal waters firsthand, where naturally heated river water flows at a comfortable bathing temperature. The area remains accessible throughout the year, though winter visits offer particularly striking scenery with steam rising dramatically against snow-covered surroundings.

The observatory is located approximately 2.5 kilometers from central Noboribetsu Onsen, reachable by local bus from JR Noboribetsu Station or on foot for those comfortable with the uphill walk. Entry to the observation area is free of charge. Visitors should note that the pond itself is not safe for bathing due to its extreme acidity and temperature, and barriers are in place to maintain safe viewing distances.