After the Roman period, when Tongeren was allowed to call itself a municipium, the neglected site was successfully restarted in the late Middle Ages. In 1230, the Tongeren called themselves cives and burghers. Located within the Bishopric of Liège, Tongeren, as one of the 23 Good Cities, also received city rights from the Prince-Bishop of Liège with the right to build a wall and establish a city militia. This was part of the Prince-Bishop's policy to promote areas within his domain militarily and economically. The military threat from the surrounding principalities such as the County of Loon, the Duchy of Brabant and the nearby areas of the Meuse and Rhineland also required the construction of city walls. For this purpose, city walls were built between 1241 and 1290 and a city militia was established. Access to the city was ensured via six gates on the main access roads. In addition, 13 fortress towers were built, which served as bastions.
The Nusen Gate, which connected to the road to Wezet, was built between 1257 and 1264 on the remains of the Roman wall from the second century AD.
In 1344, Engelbert III van der Mark became Prince-Bishop of Liège. His accession caused great tension throughout the diocese. In 1347, the Moerenpoort was destroyed in an attack by the soldiers of the former Prince-Bishop of Liège, Adolf II van der Mark. In 1379, the reconstruction of the Moerenpoort began. The porch, to which the wooden gate was attached to close the passage, was destroyed by the French troops in 1673. Thanks to an agreement between the residents of the Beinehof St. Katharina and the troops, the Moerenpoort was protected from the French devastation.