The Lahn River flows through Gießen, but not through the city center, so you won’t see the river unless you go looking for it.
The Lahn is a popular river for canoeing, and for cycling along the banks. At Lahnstein, about 140 km downstream from Gießen, the Lahn empties into the Rhine.
High above the confluence of the two rivers is Lahneck Castle, dating from the year 1226. I haven’t been there lately, but forty years ago one of my sons and I took a tour of Lahneck Castle, conducted by a teenage girl who lived nearby and was a friend of the children who lived in the castle.
For 31 months from January 1977 to the end of July 1979, Giessen did not exist as an independent city, because it had been forcibly merged with the nearby city of Wetzlar (17 km downstream) to form the combined city of “Lahn”.
The authorities even started issuing automobile license plates beginning with L for Lahn, which for some reason provoked bitter complaints among the local residents. Currently, the license plates again start with GI for Gießen or WZ for Wetzlar, and the letter L (since German reunification) denotes cars from Leipzig.
Neither the Giessonians nor the Wetzlarians (if I may coin two terms) were at all pleased with the merger of their two cities. After numerous public protests and a lost election for the party that did it, the merger was revoked as of August 1, 1979.
My photos in this post are from 2004. I revised the text in 2021.