The Bodensee-Radweg is a 260 km cycling route that loops around Lake Constance through three countries — Switzerland, Germany, and Austria. The Thurgau section runs along the entire south shore from Kreuzlingen through Romanshorn and Arbon to Rorschach, mostly on a dedicated path or quiet farm road, paralleling the lake within sight of the water for most of the distance.
The 65 km Thurgau leg makes a comfortable day's ride or a slow two-day trip with a stop at one of the lakeside guesthouses. Bike hire is available from Kreuzlingen and Romanshorn stations; SBB will move your bike between major stations cheaply. The route is flat and signposted in both directions; high season is May through September.