In a piece about our recent trip to Greece and Italy, I wrote:

Traveling from one country to another in the European Union is such a pleasure because you don’t have to stop for immigration and customs every time you land in a new place. And because they all use the Euro, you don’t have to exchange money for the local currency or remember what the different conversion rates are. It’s as easy as traveling between states here at home.

Loyal reader Dave Aronson sent me this correction:

I think you’re conflating it [the EU] with the Schengen Zone (no border passport checks) and the Euro Zone (use of Euros). These are three different sets, though they mostly overlap.

I’d never heard of the Schengen Zone, but I stand corrected. Thanks, Dave!