Koppenbrühlerhöhle, Natural monument cave in Obertraun, Austria

Koppenbrüllerhöhle is a cave in the Dachstein massif in the municipality of Obertraun, Upper Austria. Its known total length is 4054 m, of which 565 m are developed as a show cave. Cave streams flow through it, and after heavy rain large volumes of water rush out of the entrance, producing a roaring sound inside the mountain.

The cave was formed by water flowing through limestone over millions of years. In the 1700s, the space provided refuge to Franz Engl, a deserter who received supplies from a friend.

The cave's name comes from the roar of floodwaters that surge through it after heavy rain, and from the Koppen area on the upper Hallstättersee. A travel guide of 1820 already called it a famous show cave, and locals likely guided visitors for payment before it opened as the Gmunden district's first show cave on 4 August 1910.

The cave stays cold year-round and visitors should bring warm clothing for any visit. Guided tours operate during summer months and lead you through the main passages and chambers.

When snow melts or heavy rain falls, a dry cave chamber can become a rushing stream in just minutes. This rapid change shows the power of water moving through the underground passages.