The city of Bonn is on the Rhine River at kilometer 655, which is the approximate distance from Lake Constance (Bodensee), where the numbering begins.
Between Lake Constance and Bonn, the Rhine has been joined by numerous tributaries such as the Aare, the Neckar, the Main and the Mosel (to mention only the largest), so it has a width of about 400 meters by the time it gets to Bonn.
The Alter Zoll in Bonn is a place where an old tollhouse used to be. It is now a lookout point on the remains of some old fortifications, near the Rhine River.
Between the walkways going up to the lookout point, there is a monument to the German author Heinrich Heine (1797-1856), who studied at the University of Bonn from 1819 to 1820. By all accounts, Heine was not happy in Bonn, since his progressive ideas were viewed with suspicion by the arch-conservative professors.
The riverbank is an appropriate place for the monument, because Heine also had other connections to the Rhine. He was born in Düsseldorf, which is on the Rhine about 90 km north of Bonn (downstream). His most famous poem, the Loreley, is about the Rhine, as is one of his best works of fiction, The Rabbi of Bacharach.
Looking north from the Alter Zoll, we can see the Bonn opera house on the left and the Kennedy Bridge crossing the Rhine on the right.
My photos in this post are from 2006. I revised the text in 2020.