Dear crissorrir:
As others have said, in this case it refers to a group of people, things, or places, which are plural.
Here are some examples.
People: The Japanese, the British, the Africans. The rich, the poor, the old, the young, the unemployed.
Groups of Islands: The West Indies, The Canary Islands, The Hebrides, The Bahamas, The Azores.
Groups of Lakes: The Great Lakes; The Lake District, The Connecticut Lakes, The Seven Rila Lakes, The Finger Lakes.
Ranges of Mountains/Hills: The Rockies, The Alps, The Pennines, The Urals, The Harz Mountains.
Places: The United States (of America), The United Kingdom (of England, Scotland, Wales, and Northern Ireland). The United Arab Emirates.
But there are also many singular proper names where we use �the �.
Rivers: The Thames, The Seine, The Volga, The Danube, The River Nile, The Amazon River, The Tagus.
Seas and Oceans: The Pacific, The Atlantic Ocean, The Caspian Sea, The Sea of Azov, The Kattegat.
Canals: The Erie Canal, The Suez Canal, The Panama Canal, The Manchester Ship Canal.
Other Geographical Features on the Coast: The Isle of Man. The Straits of Magellan. The Gulf of Mexico. The Bay of Biscay. The Cape of Good Hope. The Iberian Peninsular.
Public Buildings: The British Broadcasting Corporation, The Eiffel Tower, The Alhambra.
Hotels: The Waldorf Hotel, The Hilton, The Sheraton Hotel.
Museums: The British Museum, The Van Gogh Museum, The Louvre.
Cinemas: The Odeon Cinema, The Rex, The Picture Palace.
Theatres: The Globe Theatre, London, The Sydney Opera House, The La Scala, Milan.
Libraries: The British Library, The Library of Alexandria, The Vatican Library.
Bridges: The Golden Gate Bridge, San Francisco; The Tower Bridge, London; The Sydney Harbour Bridge.
Landmarks: The Pyramids. The Sphinx. The Colosseum of Rome. The Hanging Gardens of Babylon.
Ships: The Queen Elizabeth, The Titanic, The Bismark.
Planes: The Wright Flyer, The Spirit of Saint Louis, The Bl�riot X1.
Newspapers: The Guardian, The Times of India, The Washington Post.
I hope this is of help to you.
Les Douglas
