Add another cities/states/region

I would like to have three/four options for agents to chose for a listing;
1. region
2. states/provinces
3. cities
4. optional

How can I achieve this? I would like to manage regions as well, just like the cities now. One is parent and child to the other.

Hi,
In OS Property, there are 3 levels of location. They are country, state and city. We can't add any object (region..etc) into this structure, because it will need very much modification on OS Property.
Moreover, in component, Region is text box fied and administrator/agent can enter the text into it
Thanks
Dam

OK, thanks for reply