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the world
If you really want me to spoil it for you, it is supposed to look like a map of the world.
The wall is a map of the world so just look at a map when you do it.
u have to get all 30 codex pages and put them on the wall in ur villa then arrange them to look like a map of the world
you would take a strip of sheet metal and a scissor-jack type mechanism....in short look up codex page 13
Err... It's just a blank wall with spaces for Codex pages to be placed, I can't "gif" a link but it's pretty obvious. Afterwards it is arranged into a map only visible during eagle vision.
For the align wheel Codex Page puzzle, look at the pictures. There should be at least one key, such as 9=1. Align 1 to 9, and then type in the code.
http://mycheats.1up.com/list/image/3170852/1/1/assassin_s_creed_2/xbox_360 There's a map of Monterigionni. Also somewhere in the site are other guides for solving the codex pages, etc. Give it a look.
Assassin's Creed 2 is different than Assassin's Creed 2 Discovery but look foward for Assassin's Creed 3 which starts on the American Revolution everybody knows about it.
The codex pages arrange to look like a world map (of Earth, not the game world) so you should be able to figure it out with a standard map. There are a lot of pictures, though.
Probably the graphics
look for the apples in each picture