This 3.4km long trail begins just two kilometres south of Esch-sur-Alzette town centre, at the Ellergronn nature reserve HQ. There are several different walks for visitors to choose from, but our focus will be on the circular route around the ponds. A fairy-tale forest stretches before us, with its dose of mystery, dancing shadows, ancient trees, pools and ponds.
We first glimpse the Hénzebiergweier through the branches before it is gradually unveiled. This body of water was formed following the collapse of an old mining gallery below it, creating what we call a funnel pond. The water comes mainly from rainfall, but karst springs are also likely. The pond is bordered by common spruces on one side and European larches on the other. It rarely gets full sun exposure, which prevents it from drying out in summer.
There are views here to surprise even the most seasoned hiker. The inky-black pool sitting majestically in the middle of the forest gives an impression of absolute calm, eternity itself. Mystery and magic, too, as the dark, immobile water reflects the foliage of the trees above. The colour palette is unusual: apple green leaves, in striking contrast with the deep black of the pond.
The trail circles a large part of the pond, allowing us to admire it from various viewpoints. We can linger at its foot, soaking in the special atmosphere of this unusual forest. A little further on, an information panel describes how the pond is home to rare flora and fauna, including pool frogs, underwater algae, reeds and European speedwell, as well as duckweed, common frogs, crested newts, Nuphar lutea – large, floating, heart-shaped water lilies measuring four to five centimetres in diameter with golden-yellow flowers emerging a few centimetres above the water – and the common rudd, small freshwater fish. Depending on the season, it is not uncommon to see a host of dragonflies, the most common being Sympetrum sanguineum, Aeshna cyanea, Anax imperator and Somatochlora metallica.
Next, the trail takes us to the small “Delsterbësch” spring, where we’re tempted to cool off in the fresh water.
Nature-friendly forest management
As we make our way towards the second pond, an information panel draws our attention to the management of this forest, characterized by its great diversity of species. The focus is on maintaining harmony with nature, considering the needs of both humans and the environment. Natural regeneration is therefore promoted, along with protecting the soil, water, and climate. It is not surprising to learn that this walk takes us through a Natura 2000 area, called “Esch-sur-Alzette Sud-Est – Anciennes minières / Ellergronn”. This stretches for 1000 hectares, making it one of our largest EU Natura 2000 protected areas.
The second pond that features on this walk also promises an extraordinary visual and sensory experience. This body of water, which developed over an old collapsed gallery, is fed by a spring, extending to a depth of ten to twenty metres. It is remarkable for the huge number of amphibians living here, not to mention a host of insects, fish, and aquatic plants. Newts reign supreme: alpine newts, palmate newts, crested newts.
Tearing ourselves away from the pond, heads filled with images, we return to the starting point of our walk: Ellergronn visitor centre, which has permanent exhibitions on the natural heritage of the Mining Basin and use of old mines, along with temporary exhibitions as part of a varied programme. After this nature walk, we can take a breather in “an der Schmëdd” restaurant, which gives local and traditional specialities pride of place.