The screenshot is a fine example of this. Sure, it looks like Gilneas, but it's actually a little pocket of Blasted Lands southwest of the Dark Portal. Unfortunately, I was on my Horde warlock when I happened upon this little coastal settlement, so its inhabitants were less than friendly to me!
What are your favorite zones to quest in, and what makes a great questing zone? For me, the vital components are atmosphere, looks, convenience of travel and geographical layout, and quality of quests. A zone has to look good -- my preference is for dark, mysterious zones like Duskwood -- and have a great feel to it. I think the feel is some combination of continuity in the looks and the quest content, plus a sense of what's going on in the zone, a bit of a story that I'm part of. Travel has to be convenient -- in long, thin zones, there has to be a way to get around. Obviously, this is tantamount where you can't fly!
And the layout of the quests has to be convenient, too. I hate doing a whole bunch of quests in one area and then moving to another area, only to have to go back to where I started. And having to go back to the same place again and again. That's just me, though. And lastly, the fewer "bring me nine basilisk gizzard" quests, the better. I don't care if they're to make your soup or for a satanic ritual -- it's still dull!
Badlands, since its Cataclysm rework, has some amazing quest lines -- it's now on the list of vital places I'll always level through -- but visually, it doesn't do it for me. My favorite? Duskwood, by a long shot! How about you?