The World of Xanth by Genjuro
If Taws is my favorite builder then Genjuro is a very close second. His areas are often complex, difficult, and richly detailed, as well as being somewhat unique of theme. One of the best examples of his unique complexity are the worlds of Xanth.
This "small world", which resides in the north woods, could easily be the largest area in existance, if you don't count each part as a seperate area. The entire affair seamlessly flows from one area to another, making it appear to be just one big area. This seamless integration - which is missing from many areas - makes this one of the more enjoyable places to explore and adventure. There's genuine adventure here to - attacking some things means near certain death, all the way up to near hero levels, while attacking other things is fairly simplistic and possible even for a comparativly low-level.
That's part of what makes this area a very good (if not great one): Your constantly on edge. One moment your dropping a Nymph for 1 exp; the next you run into the Gap Dragon and die in 5 hits. Since your always on edge, you end up being rather tense - always ready to flee, or fight. That's why I urge you to explore this area, fully - to find all the wonders and joys - and to expirance a rush of fear from an area, something which is wholly unique for me.
Suggested levels: 35 - 45. Bring a freind for
even mroe fun - and keep ya finger on the flee key :)