There are few places in the world where a wrong turn can carry quite so much history. At Nova Gorica train station, if you walk out of the west exit, you find yourself in the town of Gorizia, in Italy. If you take the east exit, you are in Nova Gorica, Slovenia.

Today, these are two sides of the same city, and you cross the border with no checkpoints, no questions asked. It’s hard to reconcile that ease with what came before. This same border was a brutal frontline during World War I,…