The city wall, which was initially built around 1220 only around the core city, made a bend to the west at the mouth of the Niederbach and ran from there across the slope of the Niederbach up to St. Martin's Church. In this section of the wall, the Cologne Gate Tower secured the road that led north from Oberwesel. At that time, this important trade route from Mainz to Cologne had to be led over the heights between Oberwesel and St. Goar, because road construction along the Rhine was not possible due to the steep bank rocks. This explains why the Cologne Gate Tower is located so far from the banks of the Rhine. It takes its name from its destination, Cologne, because the old Roman road, which once connected the legionary camps of Mainz and Cologne, led through this gate. After the expansion of the city around 1350, the same function that had previously been performed by the Cologne gate tower was now taken over by the Koblenz gate tower. Today's royal road, the old "via regia" led straight from the Cologne gate tower through the Koblenz gate tower to the heights. Above the gateway, which was built at an angle due to the old street layout, rises a shell tower with four stories. Hooked stones on the outside of the gate and hinged stones on the inside show that the gate could be secured by a portcullis and a gate. As in the case of other shuttering towers, a wooden battlement used to surround the top floor in front of the windows. The beam holes still show this. Today, the rear wall is closed with modern half-timbering. The tower is privately owned and cannot be visited.