U.S. Passport. Trusted Traveler Program card (NEXUS, SENTRI or FAST) (see below) U.S. Military identification card when traveling on official orders, or. U.S. Merchant Mariner document when traveling in conjunction with official maritime business.
The Schengen area comprises 27 European countries. There is normally no passport control on the borders between these countries. If you have a valid visa or residence permit in one of these countries, you can also visit the other Schengen countries.