I want to design a city using a game's map editor

I have vivid, reoccurring dreams that take place in a crazy city. I want to try to recreate as much of it as I can using some type of software. I figured some type of map editor or sandbox game would be the best way to go. I have almost no experience when it comes to modding, modeling, map editing, etc. so I am kind of starting from scratch. I would like the city to be one continuous piece, and not a bunch of seperate maps. Anyway, any pointers would be greatly appreciated. Also, not trying to have the city complete within a year, just want to have my software how I like it and be proficient with the tools. The city may take me the rest of my life! Oh, minecraft and it's clones are out as well. Can't stand the style, need more detail.