An establishing shot in film and television sets up, or establishes the context for a scene by showing the relationship between its important figures and objects. It is generally a long- or extreme-long shot at the beginning of a scene indicating where, and sometimes when, the remainder of the scene takes place.
Establishing shots may use famous landmarks to indicate the city where the action is taking place or has moved to, such as Big Ben to identify London, Sydney Opera House to identify Sydney, the Eiffel Tower to identify Paris or the Las Vegas Strip to identify Las Vegas.

http://en.wikipedia.org/wiki/Establishing_shot