You want to create an export with just place records and that is NOT easy.
In the family tree that you want the place records exported from, create a Person filter >> General Filters >> Everyone. In the Define Filter screen, check the box to Return values that do not match the filter rules.
Create the same type of filter for Notes.
Making the Gramps XML (family Tree) export, put this filter as the Person Filter. Set the Note filter. Make sure that the Reference Filter is set to Include all selected records.
The export should be everything with all the people (and families) and Notes already deleted.
The only way to get rid of all the other parts of the database (Sources/Citations, Media, etc ) is to manually delete those components. The goal is to get down to a database that only contains the place records
Something you could try is making all the other records Private. I discussed it here for a specific event type.
Going this route, you could make all the events with the same Type before making them all private.
As I said, it is not easy to strip out everything leaving just place records.