Europe:From this morning it will be possible to travel more than 4,000km from Tallinn in Estonia to Lisbon in Portugal, without showing a passport once.
The "Schengen zone", within which people can travel without showing passports and of which Ireland and Britain are not members, extends today to a group of mostly east European states: Poland, Estonia, Lithuania, Latvia, Hungary, Slovenia, Slovakia, Malta and the Czech Republic.
The move will boost business and tourism, but some in western Europe fear the enlarged zone will increase crime or that the EU's new external borders will be less secure.
The "Schengen zone", named after a Luxembourg village where a first agreement on passport-free travel was struck in 1985, will now cover 24 countries.
It will include an area about a third the size of the US, home to 400 million people. It will first cover land and sea borders and be extended to airports from next March.
Some border towns, including those which have been split right down the middle, held celebrations yesterday to mark the event, although since the enlargement of the European Union in 2004 travel across borders has already become much simpler.
Security has been strengthened on the EU's new external borders, although some still fear this is not enough.
"We must conclude that there will be more property crime in the border area.
"Also, the question of people trafficking will become acute," said German police union chief Konrad Freiberg in a recent newspaper interview. He bemoaned a reduction in German police strength, but said co-operation with Polish colleagues would improve over time.
He said the expansion of Schengen could maybe have waited until all the security issues had been fixed.
Cyprus, which also joined the EU in 2004, has asked for a year's delay before opening its borders.
Romania and Bulgaria, which joined the EU this year, have yet to meet security criteria.