After Wetzlar, the valley of the Lahn gradually narrows and at Leun enters the Weilburger Lahntal.
The Weilburger Lahntal belongs to the larger Gießen-Koblenzer Lahntal physiographic province, considered part of the Rhenish Slate Mountains.

In the upper area of the Weilburg Lahntal (the Löhnberg Basin) are mineral springs, such as the famous Selters mineral spring in the municipality of Löhnberg.
In the lower area, where the river turns again to the south, the Lahn is entrenched canyon-like below the level of the surrounding geographic trough.

The city of Weilburg is wrapped by a marked loop of the river.
The neck of this noose is traversed by a boat tunnel, unique in Germany.
A little below Weilburg, the Weil, originating in the High Taunus, enters the Lahn.
After Wetzlar, the valley of the Lahn gradually narrows and at Leun enters the Weilburger Lahntal. The Weilburger Lahntal belongs to the larger Gießen-Koblenzer Lahntal physiographic province, considered part of the Rhenish Slate Mountains.
In the upper area of the Weilburg Lahntal (the Löhnberg Basin) are mineral springs, such as the famous Selters mineral spring in the municipality of Löhnberg. In the lower area, where the river turns again to the south, the Lahn is entrenched canyon-like below the level of the surrounding geographic trough.
The city of Weilburg is wrapped by a marked loop of the river. The neck of this noose is traversed by a boat tunnel, unique in Germany. A little below Weilburg, the Weil, originating in the High Taunus, enters the Lahn.
Lahn