Großkrotzenburg sits at a turning point of the Roman frontier. Here, on the Main east of Frankfurt, the river border that ran north from Miltenberg came to an end, and the Limes turned away from the water to head north across the Wetterau toward the Taunus. A fort guarded the spot, with a civilian settlement, and parts of its walls and gate can still be traced in the old town, where the fort's outline is marked in the streets. The site belongs to the UNESCO Frontiers of the Roman Empire, and the local museum displays finds from the fort and the vicus.
The area today is a mix of small towns, gravel pits turned into lakes, riverside meadows and, rather incongruously, a large power station on the river at Großkrotzenburg, whose chimney is a landmark for miles around. Seligenstadt, a few kilometres upstream, is a charming town with half-timbered houses and a Carolingian basilica founded by Einhard, the biographer of Charlemagne, who is buried there. Hanau, a short way downstream, is the birthplace of the Brothers Grimm, and the German Fairy Tale Route starts there.
The riding here is flat to gently rolling, with roads along the Main and across the plain, moderate to heavy traffic near Frankfurt and Hanau, and plenty of cyclists along the river. For more interesting riding, head east into the Spessart, a forested upland with winding roads, or north into the Vogelsberg, an extinct volcano with a network of quiet, curving roads through farmland and forests.
Großkrotzenburg has fuel, shops and cafés, and Kahl am Main and Seligenstadt, nearby, have more choice. Local food includes Hessian specialties such as Handkäse mit Musik, a tangy sour-milk cheese marinated with onions, Grüne Soße, a green herb sauce from Frankfurt served with potatoes and eggs, and Apfelwein, the local cider, drunk in traditional taverns from ribbed glasses.
Spring, with the river meadows green and full of birdsong, is the nicest season here. Summer evenings by the lakes are pleasant, with swimmers and picnickers. Walk the outline of the fort in the old town, then ride upstream to Seligenstadt for a coffee in the shadow of Einhard's basilica.