Behold, in Linz, the church where the great composer Anton Bruckner worked as an organist — in the city that Adolf Hitler considered his hometown. (Hitler had big plans to make the city the cultural capital of the Third Reich.) Observe, in the streets of Salzburg (taking care to get out of the way of the glut of tour buses on their “Sound of Music” circuits) the many Stolpersteine, or stumbling blocks, embedded in the roads — a powerful art project of commemoration devised by Gunter Demnig and spreading throughout Europe, in which small bronze cobblestone-size squares mark the lives of individual victims of Nazi persecution, Jewish and otherwise.

Then Mr. Einfalt performed the great mitzvah of bringing us to the Salzburg Synagogue for a meeting with 101-year-old Marko Feingold. Speaking in a strong voice, with translation courtesy of our guide, and standing with posture better than mine, Mr. Feingold told the tale that he has told 1,000 times and that can never be told enough — not only of how he survived four concentration camps, but also of how he helped smuggle dazed, displaced Jews out of Austria and into Italy after the war. He didn’t happen to mention that the synagogue in which he stood had been vandalized most recently in 2014. And in 2013 before that.

Stepping outside again in the thin Salzburg sunlight, those with the heart for it could buy chocolates wrapped in dainty, shiny paper near the house where Mozart was born before they boarded the bus.

And then it was back to the boat and on to Regensburg, Bavaria, where Oskar Schindler lived, and Pope Benedict XVI, too. A Jewish community thrived there from the Middle Ages until they were expelled in the early 16th century and their neighborhood destroyed. Document Neupfarrplatz, a sensitively designed underground museum, incorporates excavated relics from Jewish and, before that, Roman times — and leaves in place a Nazi bunker.

I was grateful for the extended Danube shipboard time necessary to reach Nuremberg, the final destination on our Jewish heritage journey and our point of debarkation. The deft engineering maneuvers required to navigate the monumental and ingenious Main-Danube Canal through 16 locks fitted the emotional maneuvers I was working to execute, too, in order to absorb all of the schnitzel and Linzer torte, the soft towels and hard history, the beauty and the cruelty that marked this trip.

In Nuremberg, we had one last choice to make: medieval tour or World War II sites? And so my affinity group boarded a coach, one last time, to see for ourselves: first the deteriorating never-finished Congress Hall, in which Hitler planned to rule his Reich; then the Nazi rally grounds where tens of thousands who allied themselves with evil assembled (and the filmmaker Leni Riefenstahl turned architecture into visual propaganda); and, finally, to Courtoom 600 in the Palace of Justice, where a handful of those in charge of evil were tried.

The weather in Nuremberg was ugly, the sky thug gray. History felt like a vise. And the feeling of relaxation that comes with being on holiday, safe and pampered, was undone by an existential agitation. How could it not be?