The Kuhkopf-Knoblochsaue is the most compelling reason to visit Riedstadt, and one of the finest wetland reserves in central Germany. The 2,400-hectare reserve stretches along the old Rhine arm between Erfelden and Stockstadt, encompassing ancient floodplain forest, oxbow lakes, meadows that flood every winter, and patches of wild orchids that emerge in late spring. The combination of standing water, dead wood, and undisturbed vegetation creates a richness of wildlife you won't find anywhere else close to Frankfurt.
The birdwatching is excellent throughout the year but peaks in spring, when white storks return to nest on the wooden poles set up for them near Erfelden, kingfishers dart along the shaded water channels, and up to 250 species have been recorded in the reserve over the course of a season. Herons, cormorants, oystercatchers, and various warblers are easy to find. In summer the grasslands attract butterflies; in autumn the woodlands fill with fungi; in winter the flooded meadows draw wildfowl.
Walking trails run throughout the reserve. The most straightforward access from Riedstadt is via the pedestrian footbridge from Erfelden, which crosses the old Rhine arm directly onto the Kuhkopf. A circular walk of about eight kilometres takes in the main habitats. The environmental education centre (Umweltbildungszentrum) at the Erfelden end has maps, displays explaining the reserve's ecology, and seasonal wildlife guides. Cyclists can follow the Rhine Cycle Route (EuroVelo 15) along the embankment, with the reserve to one side and wide views across to Rheinhessen on the other.