Hmm... well, if I had to choose, probably the ruins of Lefay. The entire area was woven together by powerful magic, and every room had a rich history to discover. The architecture was especially beautiful, and it didn't hurt that it was full of incredibly pure water.

[The fact that the water was still pure at all given the number of powerful hellions lurking about spoke volumes of the power of Amenoch, and of the guardian seraph watching over it.]