How do film producers and crews film movies based on entire or just a proportion of towns and cities (real cities and towns)?

Question

This has baffled me as to what film producers do to film a movie or an episode based on an entire city.

Examples of this is as seen in the movie Day after tommorrow where a tsunami hits the city itself, and the city is caught on camera from above being submerged.

In White House Down, this is another prime example because the White house itself is in the city of Washington DC. How did they manage to film something like this in a settlement that looks just like the city itself?

In Charmed(series), this is another one because demons roam the streets and the surroundings is a city. The film producers use proportion of the city. I do believe the opening scene of the large proportion of the city was just shot in either a plane or a helicopter that flew around the place.

Divergent (and the other movies in the same story) is also filmed in the *Chicago City Experiment (basically the city of Chicago) and the people inside it.

How do film producers film movies based on entire or a proportion of towns and cities?

Answer 1

Many different ways:

1. Actually use the location

   The easiest and simplest - although it can also be expensive and restrictive.

   For example - for 28 Days Later, they used the real London - but were restricted to shooting at sunrise before rush hour.

2. Use a substitute

   Vancouver is used as a substitute for many cities TV shows, such as The X-Files - because that was where the show was filmed and it was easier/cheaper than flying the production crew and cast out to the real locations.

   Montreal is also a popular stand-in for several American cities in many movies - for a variety of reasons, including cost, amenities, and ameniability of the council to shutting down sections of the city.

   Other reasons for substitution are things like period dramas - glass and steel towers don't fit in well with Regency dramas.

3. Sets

   The studio would build a street set to mimic a real city location. Or just use a standard street set (redressed so it doesn't look exactly the same in each show/movie).

   Long shots of the city would be used to establish "this film is in New York", but the street-level shots could be anywhere there is a studio or soundstage.

4. CGI

   Becoming more common - actors can play against green screens, and artists can draw in a realistic backdrop based on actual photo locations.

Answer 2

In addition to HorusKol's excellent answer, I want to point out that the wide shots showing the entire city do not make up the entire movie. Just a few "establishing shots" of the whole city at the start of the film, or at the start of various scenes, gives the audience a sense that that is where the following action is taking place. Then, the film can cut to shots of actors in front of generic locations that look like cities - whether they are actual cities, the back lot of a movie studio, or even an indoor set on a sound stage that is built to look like it's outdoors.

So, to use an example from the OP's question, The Day After Tomorrow showed a lot of establishing shots of New York City ... and then moved the actors into the public library. I can almost guarantee that what looked like the interior of the public library was actually a set. But the audience watching the film sees them running through New York City to avoid the wall over water coming towards them, and sees the actors run into the public library, so they believe that the actors are now in a building in New York City. Even though it's a set they built in Hollywood.