In v201311 we changed how the API returns locations to:
More granularity in targeting Streamlined code paths Increased flexibility for handling location objects
Along with the update to location objects, we've also expanded the list of targetable locations far beyond what was previously available. If you look at new Geo_Target table - which replaces the individual City, Country, Metro, Postal Code, and Region tables - you’ll find that you now have far more control over where your ads will serve. In the past, the smallest location you could target was a city; now, you can target something as specific as an Airport.
look at this Python example that pulls down the targetable City locations.
ParentIds field, which yields a list of parent location IDs that encompass a child location.
Nicholas Chen , DFP API Team
