Rheintorturm (Konstanz)

In addition to its task as a defense tower, it also took on the function of a bridge gate.
The wooden Rhine bridge led directly through the Rheintor tower. For centuries, the bridge and the Rheintorturm were the link for traffic from the entire northern region, to the Thurgau south of the Rhine and thus to Switzerland.
For this reason, the Rheintorturm is the last standing witness to the importance of the former episcopal and imperial city of Constance as one of the most important transport and economic centers of the late Middle Ages, alongside the medieval department store (council building) at the port.
Since the Rheintorturm was built around 1200, i.e. in the Staufer period, this gate tower not only represents an imposing fortification, but also a first-class traffic monument of the medieval city of Constance. Three times Emperor Friedrich II is the city of the empire during his visits to his city ridden through this gate.
Source: rheintorturm.de/de/rheintorturm.php

This city gate used to be the only access to the city from the north across the Rhine.

The Rhine begins here (kilometer 0)