The Schengen Area is the area comprising 26 European countries that have abolished passport and any other type of border control at their common borders, also referred to as internal borders. It mostly functions as a single country for international travel purposes, with a common visa policy.
While visiting friends in France a few years ago, we passed the checkpoint between France and Switzerland several times a day and didn’t even bother taking our passports with us. It felt weird but good. (via @neilhalloran)