I am curious as to why you would want to do this? If it is to save on frame rate, there are better methods.

Keep in mind that you would have two options, levels and zones. Levels would be a little bit faster than zones but in reality it would create a very noticeable freeze in the game as you switched between either a level or zone therefore ruining the illusion that you are traveling down a street in a neighborhood.

If you are wanting to save frame rates then just keep track of your players position and create and destroy sections of your city as the user travels near or away respectively.

Keeping skills while traveling from level or zone to zone is documented in other ares throughout the forum. do some searching and you will find many examples.

Good Luck!