In a wordpress site, I have the need to assign an "area" for each post. Areas has three levels. City -> Position -> Area like "Athens -> Center -> Sintagma". Users must be able to filter all "Athens" or all "Center" or specifically all "Sintagma" posts. What is the best way to do it? Adding a custom field? Please explain with as many details as possible. Don't forget that I need to use this and filter posts. Also, if I have to pay for a commercial plugin its ok with me. I prefer to have everything setup in control panel, I dont like to write custom php code.