Draenor itself is absolutely stunning. It's a shame they ended up not fulfilling on the potential of the expansion, it could have been so amazing. Makes me sad to know that I'll never see the inside of the Temple of Karabor, or Shattrath for that matter. Despite all that, the WoD zones all felt pretty great, and my favorite is probably Spires of Arak, must be because of the way I felt when I was playing at that time, good memories.