production design

Production Design
When Alan Lee joined the project in late 1997, Helm's Deep was the first structure he was tasked to design. At 1:35 scale, it was one of the first miniatures built, and part of the 45 minute video that sold the project to New Line. It was primarily drawn from an illustration Lee had once done for the book, though fellow illustrator and designer John Howe suggested a curved wall. Used in the film for longshots, Jackson also used this miniature to plan the battle with 40,000 toy soldiers.[12]
As a pivotal part of the story, Helm's Deep was built at Dry Creek Quarry with the Gate, a ramp, and a wall with a removable section and the tower on a second level. Most importantly, there was the 1:4 scale miniature of Helm's Deep that ran 50 feet wide. It was used for forced perspective shots,[13] as well as the major explosion sequence.[12]
The film explores the armies of Middle-earth. John Howe was the basic designer of the forces of evil. The Uruk-hai were the first army approved by Jackson, and Howe also designed a special crossbow for the characters, one without the redundancy of opening to reload, the realization of an 18th century manuscript. Also created were 100 Elven suits of armour, with emphasis on Autumnal colours due to the theme of Elves leaving Middle-earth. 250 suits were made for the Rohirrim, which for Bernard Hill, even came with leather inside. Emphasized are horses and the sun, even into their swords, which took 3-6 days to forge.[14]
The Rohirrim's capital of Edoras took six months to build on Mount Sunday, with thatched roofs, but that was simply the exterior: the buildings doubled as offices and lunch halls. The army created a road to the location, whilst the interior was filmed at Stone Street Studios with tapestries designed by Lee, and Théoden's wooden throne created by his daughter.[13] Hill endured heavy make-up for the possession scene where his skin was pulled back and released for increased wrinkles. Dourif shaved off his eyebrows and put potato flakes as dandruff in his hair for unnerving effect.
The film also provides a look at Mordor and Gondor, in terms of Frodo and Sam's story. The Barad-dûr is seen fully in a tracking shot, a design which Howe called a mockery of Gothic Cathedrals. He and Lee fully created the Black Gate, though a typo in the script made the miniature into two.[12] The Rangers and Osgiliath, the ruined city reflecting London during the Blitz.[15] The set on a backlot was based around a bridge and reused some of Moria.
source:Wikipedia