Question: The shows Arrow and The Flash take place in Starling City and nearby(?) Central City. My understanding (assumption) is that both shows are filmed in Vancouver, although each show has city shots depicting the (fictional) city where the show takes place. Arrow uses Boston for cityscape shots (no official citation, but I live in Boston and recognize the shots). What city is shown in the Flash's cityscape shots?

Answer: 
The Majority of the externals and locations for the show are filmed in [Portland, Oregon](http://www.portlandmercury.com/BlogtownPDX/archives/2014/05/15/new-extended-trailer-for-cws-the-flash) (particularly the cityscapes).

The studios in which CW films both *The Flash* and *Arrow* are based in [Vancouver](http://www.comicbookmovie.com/fansites/legendsareborn/news/?a=93953), and some minor externals are filmed there as well (anything casual and unimpressive; not to sleight Vancouver, at all!). 

[Both shows](http://arrow.wikia.com/wiki/Starling_City) actually construct their cityscapes from a number of stock-footage clips from cities around the world, including Houston, Philadelphia, Baltimore, Los Angeles, Frankfurt (Germany) and Tokyo (Japan). 

This site has a [growing list](http://www.ksitetv.com/forums/showthread.php?167647-Where-is-Starling-City) of locations that have been 'spotted' by residents.

DC/WB/CW have a lot of flexibility in creating fictional cities, and as such they can insert establishing shots that are fit for purpose. If they require a scene set in Chinatown, for example, they could simply use stock footage from a street in any number of Chinatowns across the world, or even China itself. They are not spatially or geographically bound to any sort of fidelity... so they can use *whatever they have available/what they desire.*
All of the Cityscapes of The Flash, as far as I have seen, I've seen every one< are shots of Portland Oregon. I know the Skyline, because I've lived there for 50 years. Its funny tho', The round Starlabs building is projected into the shots, and it jumps from one side of the river to the other in other shows.