Nick's Pokemon Fan Site
Pokemon Crystal Codes
First Puzzle Room
In the first puzzle room (by the entrance of the Union Room) you will see a puzzle it will say Escape use a Escape Rope then renter the room and you will se a opening.
Second Puzzle Room
In the second puzzle room (surf South of the Union Room to get to this room) you will se a puzzle it will say Flash use Flash and a tunnel will appear.
Third Puzzle Room
In the third puzzle room (the entrance to the Cave of Ruins on the Southern basement entrance) the puzzle will say Water if you have a Water Stone in your pack a tunnel will appear.