Trælborg valley lies centrally in the moraine landscape between Limfjord and Klosterhede outwash plain, and between the towns of Lemvig and Struer. The course of the Trælborg valley has been regulated. It cuts deeply into the surrounding landscape and there are many incised tributary valleys along most of its length. The valley winds through the moraine landscape with an overall east-west orientation in its central part. That part of the valley that extends to its source close to the farm Mellem Lind in the west trends broadly NW-SE. The lower stretches in the east from Gudum and pasing west of Kokholm and further to its outflow into Limfjord are quite low-lying and extend roughly north-south. River Klostermølle Å flows in this winding valley (Figure 22-1).
There are many valleys in the geopark whose origins are more or less understood. The precise mode of origin of the Trællborg valley, however, remains unclear but it is probably a periglacial valley. It was presumably formed after the ice receded from the MSL that is located about 1 km to the south. The barren landscape that was subjected to permafrost was very susceptible to erosion. Every spring the snow meltwater and rainwater would follow the same path northwards and erode down into the moraine landscape, thereby creating a large periglacial valley.