What is the term for when a scene in a film shows e.g. the Eiffel tower so that the viewer knows that the scene takes place in Paris. I know the term exists but I cannot recall it.
It's called an establishing shot.
An establishing shot in filmmaking and television production 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. - Wikipedia
Establishing shots may use famous landmarks to indicate the city where the action is taking place or has moved to, such as the Brandenburg Gate to identify Berlin, Empire State Building or the Statue of Liberty to identify New York City, the London Eye or Big Ben to identify London, the Sydney Opera House or the Harbour Bridge to identify Sydney, the Hollywood Sign to indicate Los Angeles, the Eiffel Tower and/or the Arc de Triomphe to identify Paris, the Shibuya Scramble Crossing to identify Tokyo, or the Las Vegas Strip to identify Las Vegas. - ibid