Each article to be shown to customers must generally be mapped to your internal location hierarchy; this can be done in one of three ways:

Use our location hierarchy as your primary source of IDs.
This is often inappropriate, and rarely the easiest solution to implement unless doing a completely clean-room design of a site, but is the easiest if your existing system has no concept of location today.
Perform a manual mapping of specific locations in our system to specific locations in your system.
You then have two options for how you map any given event request to a location in your system: process it on your side as a post-processing operation by walking the list of attached nodes for each event to determine visibility (easiest when you are building a search implementation that will need to parse these documents anyways) or make multiple queries to event-list, once for each of the locations.
Let us perform the manual mapping of specific locations in your system to our hierarchy.
Your feed configuration will have a parameter added for each mapping set created by us - for example, "hotel_id", "area_id", "region", etc, which will retrieve content based on your internal reference. This mapping information does not appear in the feed - it is then your responsibility to "remember" the information provided as a result of this event list. This can be done by databasing the returned event ids and storing them against your reference id, by storing resulting articles pulled down using these ids into different areas of the filesystem, etc. Should you wish to do so, the content can be further sliced by restricting it to other areas using feed parameters should you take an approach that requires that you avoid parsing event content.
Alternately, you can use any one of a set of standard mappings that we have created to ISO country codes, airports, weather station IDs, and others. However, though the codes may be supported, they may still require customisation to meet your requirements for geographical coverage and content availability.