I am going through a book called The Lord of the Rings Sketchbook by Alan Lee. He spent 6 years studying the landscape of New Zealand, architecture and other mythology (he had the experience of having illustrated the LOTR book before the concept of the movie was birthed, and also a lot of other mythological books including the Norse). In the span of six years he made 2,500 drawings, hundreds of digital works and also a lot of designs.
The whole look of the film is pretty much defined by his drawings. He pretty much designed Minas Tirith, Minas Morgul, Lothlorien, Rivendell's waterfalls and buildings, the halls of Edoras, and just about everything you saw in the film. Amazing feat I have to say.
True genius, accompanied by hard work. That is what makes it work. That's my conclusion after seeing the book.