Niji no Yu Osaka-Sayama is a highly stylish and popular super sento (large public bathhouse) in Osaka Sayama City. One of its main attractions is the scenic open-air bath, where guests can relax individually in egg-shaped ceramic tubs while enjoying the surrounding views. These uniquely shaped tubs are ergonomically designed to gently envelop the body, creating a warm and deeply relaxing bathing experience. They are collaborative works by spatial designer Kuniharu Genko and Shigaraki ware master craftsman Kazuhiro Ueda. The indoor baths are equally open and inviting, featuring a diverse range of modern designs that create a refined and contemporary atmosphere. In terms of health benefits, the facility is also exceptional. Highlights include the Radon Microbubble Bath, which uses Shigaraki ceramic plates infused with radium ore to help boost immunity, while fine bubbles soothe both body and mind and are said to enhance beauty and overall health. Another feature is the Radon Ceramic Sauna, which uses radium-infused Shigaraki ceramic sauna plates to improve thermal efficiency, promote circulation, strengthen immunity, and support beauty and wellness. When traveling by train, the nearest station is Kitanoda Station on the Nankai Koya Line, about a 20-minute walk away, making it slightly less convenient by public transport. However, for those arriving by car, the facility offers a spacious parking lot, ensuring easy and stress-free access for drivers.