"The Donnersbachklamm is a canyon near to the northern slopes of the "Rottenmanner" and "Wölzer Tauern" and  as the name is saying, is located in the district of Donnersbach. Since the year of 1991 this entire area is a natural monument, which belonges to the county of Styria/Austria. Since thousands of years the flowing water is digging this canyon through the soft stones of quartz-Phyllit crystal. Anyway, the starting point of a two hours hiking trip through this natural monument is the guesthouse "Leitner", which you can spot right at the main road. The entire walking trail of the Donnersbachklamm is marked. So you won't get loose into the wilderness." (Source: wikipedia)