Kiyotsu Gorge

▶Birth of Kiyotsukyo Gorge
16 million years ago, the eruption of an underwater volcano caused volcanic ash to accumulate on the seabed. Through chemical changes, the green color transformed, leading to the formation of green tuff. 5 million years ago, magma flowed into the layers of green tuff from underground. As it cooled and solidified, it turned into a type of volcanic rock called andesite, creating a columnar joint structure due to volume contraction during cooling. Subsequently, the region experienced a period of tectonic activity, raising the seabed to become land. The Kiyotsu River carved through this terrain, exposing the columnar joints of the underlying volcanic rock at the valley floor. As the valley deepened, the present-day Kiyotsukyo Gorge was formed. The cliffs of Kiyotsukyo consist of clusters of columnar rocks (resembling a bundle of hexagonal pencils), which, while hard, are fragile and prone to collapse. (See image below)
*1 Tuff (gyokai): Rock formed from consolidated volcanic ash.
*2 Volcanic rock: A type of volcanic rock formed from the cooling and solidification of magma. Andesite and basalt belong to the same category.
*3 Columnar jointing: A phenomenon where magma cools and solidifies, contracting to form column-like structures with four to six sides.

▶History of Kiyotsukyo
The existence of hot springs was already known approximately 300 years ago during the Genroku period. Although discussions about developing the hot springs began at that time, various issues related to the topography hindered progress for a long time.
In 1862 (the 2nd year of the Bunkyū era), a hot spring area was created by local residents. In 1941 (the 16th year of the Shōwa era), the beauty of the gorge and its columnar joint formations were recognized, leading to its designation as a national scenic spot and natural monument.
In 1949 (the 24th year of the Shōwa era), it was designated as part of the Joshin'etsu Kogen National Park, and the hot spring town was also developed.
In February 1984 (the 59th year of the Shōwa era), a large avalanche struck, causing many casualties in the hot spring town. In July 1988 (the 63rd year of the Shōwa era), a rockfall accident occurred along the Kiyotsu Mountain Trail, which runs from Kiyotsukyo Onsen to Yagisawa, leading to a complete ban on access to this path.

▶History of the Construction of the Canyon Tunnel
Following the closure of the Kiyotsukyo Mountain Trail, there were requests from local residents and tourists to provide access to the spectacular columnar joint formations at Byobuiwa. This prompted discussions between the Environment Agency (responsible for national parks), the Cultural Affairs Agency (responsible for natural monuments), Niigata Prefecture, and the former Nakazato Village (now Tokamachi City).
Considering the following points:
1. Reopening the closed pedestrian path is impossible.
2. Establishing a safe pedestrian path is difficult due to the risk of rockfalls.
3. Large-scale artificial structures that compromise the landscape are not permitted within the national park.
4. The national park is intended for broad public use, and thus should not be neglected as a tourist resource,
the decision was made to construct a "pedestrian tunnel" that allows for the safe appreciation of the gorge's beauty without compromising the appearance of the national park. Construction of the pedestrian tunnel began in 1992 (Heisei 4) (with Nakazato Village as the entity responsible for the project, at a total cost of approximately 2 billion yen). In October 1996 (Heisei 8), the Kiyotsukyo Canyon Tunnel was excavated (the riverside walking path remains closed to this day).

▶Revitalization through Contemporary Art
More than 20 years after the excavation, the number of visitors decreased year by year, falling to about 50,000 annually. To address this situation, the facilities were renewed in conjunction with the "Echigo-Tsumari Art Triennale," held every three years in Tokamachi City and Tsunan Town.
In April 2018 (Heisei 30), as part of the "Echigo-Tsumari Art Triennale 2018," the tunnel facilities were renovated, and entrance facilities were newly established (entitled "Tunnel of Light").
In April 2021 (Reiwa 3), an additional artwork was added at the second observation point as part of the "Echigo-Tsumari Art Triennale 2021." The total length of the Kiyotsukyo Canyon Tunnel is 750 meters. From the three observation points and the panoramic station at the tunnel's terminus, visitors can enjoy the stunning beauty of the gorge. Especially at the panoramic station, a dreamy art space is created by reflecting the gorge’s scenery in a water mirror. Experience the soft new greens of spring, refreshing clear streams, vibrant autumn leaves, and winter landscapes reminiscent of ink wash paintings in their respective seasons. Additionally, there are display corners in various places within the tunnel that introduce the four seasons of Kiyotsukyo and its natural history.