Well, they're going to need some serious firepower to do that, and it'll have to be an aerial detonation. Even with the Hiroshima bomb, we didn't annihilate an entire city. We sure made a mess of what wasn't vaporized, but we didn't destroy it entirely.
Unless, of course, they're talking about a "city" on the scale of Sierra Madre (which is only 3 square miles). In that case, I would probably recommend Pomona, California. Hell, it'd probably do about $2 billion in improvements...
In other words -- and this is for the al Qaeda creeps -- shut yer freakin' pie holes. You're all a bunch of wussified cowards whose existence only verifies the presumed love that Hitler had for water buffalo. Kiss my American butt.
Cities like LA are so big, even if we allowed them eight weeks free reign, they couldn't put a dent in it. LOL!