Picture is of the entrance, no cameras are allowed in the onsen.

Very rustic and traditional, yet comfortable and satisfying onsen nestled in a corner of Zao Onsen Town. Natural hot water flows down from the mountain, with a strong hint of sulfur and other minerals. Definitely good for the skin and body. Entrance fee was 700yen, with towels costing I think 300yen extra and lockers 100yen. Try to bring your own towels! I visited around 5.30pm and stayed till 6.30pm, they were still open. The air was cool as it just rained, and the warm-but-not-too-hot onsen waters provided a comfortable contrast to the cool crisp air. It was a truly relaxing experience as I breathed in the fresh mountain air while watching water rush through the onsen and down a small stream, while being immersed in the hotel water myself. Definitely recommended for daytrippers. Easily among my top 5 onsen experiences.