Uramigataki Onsen is a free, wild outdoor hot spring located next to the 35-meter Uramigataki Waterfall in the Nakanogo area of Hachijojima Island, Tokyo, surrounded by subtropical primeval Hego tree fern forests. Hachijojima is a volcanic island floating approximately 287km south of Tokyo and about 75km south-southeast of Mikurajima Island. The name Uramigataki (Back-view Waterfall) originates from the unique landscape where the waterway path passes behind the waterfall, allowing visitors to view it from the reverse side. This waterfall forms where the Mihara River intersects with Nakanogo's rice paddy irrigation canal, creating a beautiful scene where sunlight filters through the cascading water like a shower. After a 10-minute walk along the trail, visitors can bathe while viewing the waterfall from behind as it flows down the rocky cliff. The spring water is classified as sodium-chloride strong salt hot spring (Nakanogo Ogoshi Onsen) with a source temperature of 53.1°C, pH 6.3-6.7, and an abundant flow rate of 500 liters per minute. The yellowish transparent water has high salinity, warming the body effectively, and bathing in the forest while listening to the waterfall sounds is an exceptional experience. Swimwear is mandatory as it's a mixed-bathing facility, and soap and shampoo use is prohibited. A changing room and toilet are provided, with free 24-hour access available (recommended hours 9:00-21:00). There are no lockers, so keeping valuables in your vehicle is recommended. Morning hours are relatively less crowded, offering a more private experience. This unique hot spring offers an experience unlike any other in Tokyo, combining the island's rich nature, subtropical atmosphere, and the distinctive perspective of viewing a waterfall from behind. We also recommend combining your visit with nearby attractions such as Kihachijo silk dyeing workshops and Hego forest primeval areas. Note: As of 2024, there have been reports of temporary closure, so please confirm operating status with Hachijo Town Hall or Hachijojima Tourism Association before visiting.