Today is International Holocaust Remembrance Day. As a tour guide, I have an ethic that every Rick Steves bus tour through Germany includes a pilgrimage to a concentration camp memorial. It’s our hope, as guides, that with this powerful experience, our travelers will heed the collective wish of Hitler’s victims: Forgive but Never Forget. When you travel thoughtfully — and incorporate stops at memorials to the six million Jews who were murdered by Nazi Germany — the impact changes you.

If you sea...