I think the swimmers enter first
The Olympic torch relay always terminates in the central stadium of that year's Olympic Games.
At the opening ceremonies, the countries march into the stadium in alphabetical order of their country's name in the language spoken by the host country. The exceptions are that the athletes from Greece are always the first into the stadium, out of respect to the home of the Olympics, and the athletes from the host country are always last into the stadium.
The country which appears first in the Olympic Parade of Nations is always Greece, because Greece started the Olympic Games thousands of years ago. And the last country to parade is the host country.
During the Opening Ceremonies of the olympics; the athletes from Greece enter first, in honor of the original Olympics held in Greece. Then the other athletes follow by nation in alphabetical order (except for the Beijing 2008 Games where it was based on the number of characters in the country's name). The host country's athletes always come last. After the games are announced as "officially open", this is followed by the raising of the Olympic Flag. The torch ceremony then begins. The running of the torch usually begins weeks before the Olympic ceremony, transporting the Olympic torch to each country that lies between Greece and the host country. The most exciting moment of the Olympic Opening Ceremony is when the torch enters the stadium and is lights the Olympic Flame. The Flame is always kept burning until the end of the Olympic Games. For more history of the Olympic Games : http://en.wikipedia.org/wiki/Olympic_Games
The ancient Olympic Games originated from Greece; also the first edition of the modern Olympic Games was held in Athens - 1896.
The Host Country.