Around 1250, the city was expanded to the north. The suburb of Niederburg was secured by a mighty wall with seven towers and three city gates. To protect the important trade route that led to Koblenz and Cologne, the Koblenz Gate Tower was built. In former times, this long-distance road between Oberwesel and St. Goar did not run through the Rhine valley, but over the heights. The Koblenz gate tower is also a shell tower. However, the 19-meter-high tower was not placed on top of the city wall, but built in front of it, because the mistakes made when building the towers on the Rhine had been learned from. The gateway could be closed by heavy gate wings. The hinged stones can still be seen. In case of danger, a portcullis additionally secured the gate. In front of the gate was a deep moat, over which a wooden bridge led. The four floors of the tower were connected by ladder stairs. The tower was always guarded. The top floor had window openings on all sides. Through them, any movement on the street, but also any fire in the city could be detected early. Old city views show the tower with a pointed roof.