First, you have to have defeated all sixteen gym leaders in both regions. Then, travel west of Viridian City through a small path. The path eventually widens and leads to Mt. Silver.
If you're standing in the room that is the entrance to victory road, then go to the very left of the building, go out the door, and keep running left until you are at the cave entrance. On the way...
You need to get all 8 badges of Johto, all 8 badges of Kanto and have beaten the Elite 4. Once you've done that, talk to professor Oak/Elm ( I don't remember which) and he'll give you access to mount...
QUESTION BY: Licky Licky After you defeat all 8 gym leaders in Kanto, you will have to go the proffessor's lab in viridan city and he will "arange" a trip to Silver Cave.FIRST IT ISENT SILVER CAVE IF...
i think you have to beat all of the gym leaders --IMPROVED ANSWER-- You have to beat all the gym leaders in BOTH regions. Johto and Kanto. Then you go to victory road, and go left(<-- that way)...