Travellers travelling between Schengen countries but from a third country outside the territory must be subject to Schengen entry checks upon arrival in the Schengen area. The reason is that the route is outside the Schengen area and that the authorities at destination would not have the opportunity to distinguish between passengers arriving on board the origin and those who have joined the centre. In addition, travellers are required to check the schengen exit borders when they leave. In addition to having the opportunity to visit 26 Schengen countries with a single document, you can also visit other countries that are not part of that territory. A number of countries around the world allow foreigners holding multiple-entry Schengen visas to enter their territory and stay there for a limited period, say two weeks. Svalbard belongs to Norway and has a special status in international law. It is not part of the Schengen area. There is no visa regime for Svalbard, entry, stay, or work, but it is difficult to visit Svalbard without travelling within the Schengen area although there are charter flights from Russia. Since 2011, the Norwegian government has implemented systematic border checks for people wishing to enter and leave Svalbard and requires a passport or identity card for non-Norwegian nationals. As a result, the border between Svalbard and the rest of Norway is widely treated as any other external border of Schengen.  A Schengen visa must enter several times in order to return to Norway.  There is no social security or asylum system for immigrants in Svalbard, and those unable to support each other may be removed.  Of the five smallest European states, only Liechtenstein is officially part of the Schengen area.
The other three – Monaco, San Marino and Vatican City – keep an open border with one of the Schengen states. The Danish territories are not part of the European Union or the Schengen area, and visas for Denmark are not automatically valid in these regions. However, in both areas, there is no border control for arrivals from the Schengen area and air or sea carriers are responsible for carrying out pre-board document checks, as is the case for travel within the Schengen area. Citizens of EFTA countries can travel to faeces and Greenland with a passport or ID card, while citizens of Denmark, Finland, Iceland, Norway or Sweden can use any acceptable identification (for example. B driver`s licenses or bank cards that are not recommended, as planes could be diverted to Scotland in case of fog).   Since the implementation of the Schengen rules, the borders between the participating countries have been closed (and often completely removed).