Oh, that was a hard one between Sulani, Forgotten Hollows and Windenburg... But in the end I would have to pick Windenburg. I love the way the buildings and the city look. And I also love that the scenery change a lot depending on where on the map you are: In town there is the old town look, while on the island you can bulldoze the other buildings and get a lovely sea view from the cliff or by the beaches (and if I remember correctly the island no longer spawn any visitors except for those that live there), and last but not least there is the woods where the houses are far enough from each other to afford some privacy. Basically the scenery changes leave plenty of room for different kind of stories. I only wish it would be possible to swim in the sea.
And going with the idea of having 100 lots to use as I want that would give me plenty of room to build more hostels, ruins, markets, bakeries and small hidden stores selling scented candles, magic books and healing crystals ^^