I'm trying to figure out the best way to manage my controller(s) and models for a particular use case.

I'm building a review system where a User may build a review of several distinct types with a Polymorphic Reviewable.

Country (has_many reviews & cities)
Subdivision/State (optional, sometimes it doesnt exist,  also reviewable, has_many cities) 
City (has places & review)
Burrow (optional, also reviewable ex: Brooklyn)
Neighborhood (optional & reviewable, ex: williamsburg)
Place (belongs to city)

I'm also wondering about adding more complexity. I also want to include subdivisions occasionally... ie for the US, I might add Texas or for Germany, Baveria and have it be reviewable as well but not every country has regions and even those that do might never be reviewed. So it's not at all strict. I would like it to as simple and flexible as possible.

It'd kinda be nice if the user could just land on one form and select either a city or a country, and then drill down using data from say Foursquare to find a particular place in a city and make a review.

I'm really not sure which route I should take? For example, what happens if I have a Country, and a City... and then I decide to add a Burrow?

Could I give places tags (ie Williamsburg, Brooklyn) belong_to NY City and the tags belong to NY?

Tags are more flexible and optionally explain what areas they might be in, the tags belong to a city, but also have places and be reviewable?

So I'm looking for suggestions for anyone who's done something related.

Using Rails 3.2, and mongoid.