Maruonotaki Falls, standing 23 meters high and 16 meters wide, is located nearby Route 223, which connects Maruo Onsen with Kirishima Shrine. It is a rare hot spring waterfall: the water from four springs in the hot spring district upstream (namely Hayashida, Ei-no-o, Iodani, and Myoban), pools and flows together. The waterfall has an abundant water volume and powerful splash, while also being noteworthy in that the hot spring components react with light, transforming the waterfall basin into a beautiful milky blue. In the fall, the leaves change color, and in the winter, the waterfall scenery is only enhanced by the mystical scenery created by the rising steam. During the night-time illumination, the droplets reflect the lights, creating an even more fantastic, magical atmosphere.

In the past, Route 223, which leads to Maruonotaki Falls, was well-known for being a dangerous road, as it was very narrow and had multiple sharp curves. On top of that, there were frequent landslides and fallen trees, which interfered with driving. In order to ensure safe and smooth travel, they initiated construction of a bypass bridge, which was exceptionally difficult because of the severe soil alteration (a characteristic of hot spring areas). As a result, it took 14 years to complete the 302-meter-long Maruonotaki Bridge, which finally opened in 2015. This improved access by car, and provided a spectacular view of the waterfall from the car window. Maruonotaki is located on the “Maruo Nature Trail” forest therapy road, a 2.3-km track through the virgin forests of the Kirishima hot spring district. Just upstream from the waterfall, there is a stretch of stone-paved river bed that is 200 m long and 15 m wide. Called “Senjojiki,” it allows visitors to experience the mystery of nature while taking a pleasant stroll through the forest.