In the "local/data" folder, there are a few tds files that have some information about what Tableau geocodes.
You can also connect to the GEOCODING.fbd file in that folder (with Tableau) and it has an extensive list as well. The username for it is "sysdba".
(Probably C:\Program Files\Tableau\Tableau 9.0\Local\data, depending on your installation.)
Thank you I have been looking at these files. Is there a way to connect all levels of data from Country, county state/province, postcode level? for example I can see what postcodes are within Buckinghamshire in the UK I cannot seem to find a relationship between the fields
Slightly uncouth, but you could export the list to a CSV and geocode with something like the Google Geocoding API: http://maps.googleapis.com/maps/api/geocode/json?address=YO24&sensor=false
You may run into some issues where a zip code is in multiple countries - for example 0110 is in New Zealand and South Africa.