To enter any European country, you will need a passport. However, once there, travel between 27 European countries — the Schengen Agreement nations — requires no passport. Note that some Schengen Zone countries (namely Switzerland, Norway, and Iceland) are not members of the E.U., and some E.U. nations, including Ireland, are not in the Schengen agreement. Great Britain is not a member of either the Schengen Zone or the E.U. … so your passport will be checked crossing the U.K. border into any other European country. If this seems complicated, a concierge or villa specialist can help clarify any questions.