“Mëllerdall” is the Luxembourgish expression for „valley of the mills”. The name originates from the numerous mills that, in former times, operated along the river Sauer and its tributaries Black Ernz and White Ernz as well as along smaller creeks. The water that feeds the rivers emerges out of the important Luxembourg Sandstone aquifer in addition to other sandstone and dolomitic units. Today, several of these springs are used for the supply of drinking water, allowing the municipalities of the region to be nearly fully self-sufficient in this respect.

Since the late 19th century, the rocky landscape of the Luxembourg Sandstone Formation has been
touristically promoted as “Luxembourg’s Little Switzerland” (“Petite Suisse Luxembourgeoise”) and is mainly based on the picturesque landscapes. Activities such as hiking and rock climbing take place on well signposted trails and in defined areas. The sequence of different rock types has provided areas for settlement and farming and allowed the exploitation of natural resources such as groundwater or building stones. Since the Stone Age, the influence of human activity has turned the natural landscape into a cultural one, rich in biodiversity and with a large diversity of ecological niches.

The surface area of the Mëllerdall Geopark is 256 km², which is about 1/10 of the country’s total surface area. The area of the Park has a permanent population of about 23,000 inhabitants (4.5 % of the population of the country). Seasonal tourism however, especially during high season (July and August) increases the area’s population by a fivefold.

The largest town and centre of the region with 5,500 inhabitants is Echternach. It is also the oldest town of Luxembourg, founded in 698 by Saint Willibrord, a Northumbrian missionary, who established the famous Abbey of Echternach, where his remains are buried and where monks developed one of the most important scriptoria in the Frankish Empire.
The Dancing Procession of Echternach is founded on the cult of Saint Willibrord. It is a religious event, deeply rooted in regional traditions and is expressed through prayer, song and dance. Nowadays, the procession is supported by the civil and religious authorities and attracts an average of 13,000 participants each year from Luxembourg and the neighbouring regions. In 2010, the procession was included in the Representative List of the Intangible Cultural Heritage of Humanity of UNESCO.
In 1886, thanks to the invention of the lead accumulator by the Luxembourgish engineer Henri Tudor (1859 - 1928) Echternach was amongst the first cities in the world to have electrical light.

The Mëllerdall Geopark is part of the cuesta landscape of the Luxembourg Guttland, the southern part of Luxembourg (the name “Guttland” referring to the climatic and soil-conditions, which are favourable for agriculture). It is formed by sediments of Triassic and Jurassic age and is characterized by three geomorphological units, roughly differentiated into:

» the plateaus of the Luxembourg Sandstone Formation and the dolomites, extending to altitudes slightly above 400 m and deeply incised by rivers and creeks,
» gently undulating hillsides in marly substrate and
» the major valleys of the rivers Sauer and Alzette.

The lowest point of the Geopark, with an altitude of about 140 m, is located in the south-east of the area, in the Sauer valley. The rivers Alzette, White Ernz and Black Ernz are tributaries of the river Sauer. The whole area is part of the drainage basin of the Moselle river.

The annual mean temperatures in the region are 8 - 9.5 °C, with 17 °C in the summer and 0 °C in the winter in mild positions. Annual precipitation is about 700 - 800 mm. The climate is characterized by transitional conditions from atlantic to continental and is favourable for agriculture.

Mëllerdall Geopark is situated in the centre of the Trier-Luxembourg Basin, a synclinal structure of Triassic and Lower Jurassic sediments at the north-eastern rim of the Paris Basin.

With its alternation of relatively thin strata of hard and soft rocks and an inclination of less than 10°, the area forms a small-scaled cuesta landscape, developed epigenetically by the incision of rivers and by gravitational mass movements. Many forms tell their geomorphological stories and illustrate the vividness of geological processes during the Cenozoic. Numerous archaeological and botanical specifics are related to the geology of the area.

In the centre of the syncline, the up to 100 m thick Luxembourg Sandstone unit of Lower Liassic age forms one of the most spectacular and impressive sandstone landscapes in Western Europe, with an abundance of sedimentary and weathering structures on its rock faces. Its long-term storage and filtering capacities allow a nearly fully self-sufficient drinking water supply of the region.

The Luxembourg Sandstone Formation is the most important aquifer in terms of drinking water supply, with a long-term continuous discharge and excellent filtering capacities. Water from dolomitic layers of the Muschelkalk is used to a minor extent. Smaller groundwater reservoirs in limestone, dolomite and sandstone layers often run dry during the summer months, while small rivers on marly substrate run only periodically after precipitation events.

The Mëllerdall Geopark is a rural area. Land use changes depending on topography and soil types and changes depending on the substrate. The plains, plateaus and shallow slopes with fertile soils on marly or dolomitic substrate are mostly used for agriculture. Meadow orchards are typical elements of this historically grown cultural landscape. The steep slopes, mainly constituted by dolomites or sandstone, are covered by wood, mainly deciduous and mixed forests (Melico- and Luzulo-Fagetum, on regolith also Tilio-Aceretum). Ilex aquifolium is proof of the atlantic climatic conditions in the valleys. Pinus sylvestris is present on the sandy, easily parched edges of the plateaus. While Pinus sylvestris might be autochthonous, as are Juniperus communis and Taxus baccata, other conifers are of anthropogenic origin.

The region is highly regarded for its botanical specifics. Extreme microclimatic conditions along the high rock faces and in narrow gorges which tend to mimic the oceanic climate of the European Atlantic fringe, favour the occurrence of a great variety of ferns and mosses worth protecting. Some of these have one of their rare incidences in Continental Europe here (e.g. Hymenophyllum tunbrigense and Trichomanes speciosum).

The natural resources of the Geopark region have been used by man since prehistoric times. Archaeological findings show the Mëllerdall to be an important archive of the early history of Luxembourg. The oldest human skeleton in Luxembourg was found in the area, in the valley of the Black Ernz. In ancient times, geomorphological forms like ledges, rock overhangs, caves and open joints have been used as temporary settlement areas, shelter and burial grounds. Remnants of a Roman villa and some medieval castles are present and can be visited in the area as well. Today, the main settlement areas are plateaus and hillsides, as well as the valleys of the rivers Sauer and White Ernz, which are used mainly for agriculture.
Natural resources like water and building stones have been exploited by man since his early days, and today the region is nearly self-sufficient in its supply of drinking-water from groundwater. Some water is even exported to neighbouring municipalities.