The numerous mills along the Sauer and Schwarzer Ernz rivers and many other streams gave the nature and geopark its name. In the east of the Grand Duchy of Luxembourg, on the border with Germany, 11 municipalities with a total area of 256 km2 and around 26,000 inhabitants have joined forces to create the Mëllerdall Nature & Geopark.

The imposing sandstone cliffs and deep gorges are very distinctive features of the Mëllerdall Nature & Geopark. However, the nature park is also characterized by traditional orchards with hundreds of fruit varieties, large forests and a high proportion of nature reserves. The remains of the "oldest Luxembourgers" were also found here. Echternach is the oldest town in Luxembourg. The "Echternach Spring Procession", an intangible world heritage site, takes place here.

In 2022, the nature park was included in the ranks of UNESCO Geoparks. UNESCO Global Geoparks are regions with a geological heritage of international importance.

The "Felsenweg" hiking trails of the delux Nature Hiking Park lead through the Nature & Geopark.