The Schengen Area is a group of 25 European countries which have abolished all border controls between each other. It originates from the eponymous agreement signed in the Luxembourgish town of Schengen in 1985, which has since been absorbed into the European Union. All EU members except Ireland and the United Kingdom are required to implement Schengen and, with the exception of Bulgaria, Cyprus and Romania, have implemented it. Three non-member states: Iceland, Norway and Switzerland, have both signed up to an implemented the Schengen rules. As such the Area currently covers population of over 450 million people and an area of 4,312,099 km2 (1,664,911 sq mi).
Implementing the Schengen rules involves eliminating border controls with other Schengen members whilst strengthening border controls with non-member states. The rules include provisions on common policy on the temporary entry of persons (including the Schengen Visa), the harmonisation of external border controls, and cross-border police and judicial co-operation.