Rheinauen, usually called the Rheinaue, is Bonn's big riverside breathing space: a wide park of lawns, lake paths, gardens, and open views along the Rhine. It was shaped as a major garden-show landscape and still feels more expansive than a normal city park.
Come for walking, cycling, picnics, or a low-key break between museums in the former government quarter. In good weather it is one of the easiest places to understand Bonn's gentler side, away from Beethoven sites and federal history.