There is no code to Centra ruins....is there? Unless of course you're intending to beat the section with the time limit?

When you meet the first demon (above the big ol' door) he should have one eye, take it out and walk up the stairs leading away off the rigth ahnd side of the screen. Climnb up the tower there and put the eye in quickly, note down the numbers and then take both eyes out and insert them into the statue above the door again. This should then promt you to input the code. It's different every time. The boss inside is Odin, and he can be pretty powerful, mug him to get a Luck-J scroll!! ^_^; hope i was helpful!