Finding food in foreign grocery stores, or finding out that reality has fewer joints than you might think.

From the comments:

Making sense of unfamiliar legal systems

This insight also leads to a helpful lesson of just what "having an open mind to a different culture" really means. At bottom, it means having faith in the people who subscribe to the culture -- faith that these people are motivated by the same forces as we, that they are not stupid, irrational or innately predisposed to a certain temperament, that whatever they are doing will make sense once we understood the entire circumstance.