Kiyotsukyo Gorge Tunnel — Suspended Glass Platform Over Emerald River

Kiyotsukyo Gorge is a 750-meter-long ravine carved by the Kiyotsu River through solid granite, with vertical cliffs rising 50–100 meters on both sides. The gorge was inaccessible until 1996 when a pedestrian tunnel was blasted through the cliff face, allowing visitors to walk inside the mountain while observing the gorge through periodic window openings. In 2018, the tunnel was redesigned by artist Ma Yansong, who installed a mirrored stainless-steel 'Periscope' observation chamber at the tunnel's end — a polished metal box suspended over the emerald river water, reflecting both gorge walls and sky to create an infinite-mirror effect.

The gorge water is an otherworldly turquoise color (mineral suspension from upstream granite erosion) year-round, but is most vivid October–November when low water flow and autumn sunlight intensify the blue-green hue.