Bad Säckingen sits on the High Rhine at Germany's southern edge, close enough to Switzerland that a casual walk over the river becomes an international border crossing. It is a small spa town, not a major Black Forest base, but it has a tight cluster of sights that reward a spare day: the long covered wooden bridge over the Rhine, the baroque towers of St. Fridolin's Minster, and Schloss Schönau, better known here as the Trumpeter's Palace.
The trumpet theme comes from Joseph Victor von Scheffel's 19th-century verse epic Der Trompeter von Säckingen, which turned the town into Germany's "Trumpeter City." You will see the reference in statues, signs, and the museum inside the palace. It gives Bad Säckingen a local story that is more specific than the usual spa-town mix of river promenade, old lanes, and cafes.
Come for half a day if you are moving along the Rhine between Basel and the Black Forest. The centre is compact, the bridge is genuinely handsome, and the Swiss village of Stein is right across the water. Bad Säckingen is not dramatic, but it is distinct, walkable, and much better than treating this stretch of the Rhine as a blur from a train window.