Koblenz and the Deutsches Eck
One of the unique items of Koblenz is the statue and monument (denkmal) to Kaiser Wilhelm I that was erected after the unification of Germany.

This structure is accessible, and you can climb to the parapet along the top, which provides a nice view of the Deutsche Eck and the Rhein, as well as some of Koblenz to the south.

The stature on top was virtually destroyed in World War II, wth the horse and the Kaiser hanging off to the side.
To the left is a view of the actual Eck, or Corner, looking down the Rhein with the Mosel to the left.

Below left is a view back to the city, with St. Kastor's in the center.  Below right is the iner memorials of the denkmal, with each state of the new Germany commemorated.  Since my family hails from Wurttemburg, I was naturally inclined to take a photo of its coat of arms!