you have to get a key
use the basement key in goldenrod city. the key is in goldenrod.
Find the key
smash your way through the door
Go underground Goldenrod by heading North in Goldenrod. Find a narrow house with a door, go in it. If you went to the correct house, there is a staircase. Use the staircase and go south some, there should be a hallway to the east. There is a door at the end of the hallway. This is for gold, the equivilant of silver.
when you go through the route past goldenrod city you will find national park. The door stright ahead goes to the park the door to the left of the gate goes to the pokeathlon dome =]
You actually have to go through it as part of the story. Team Rocket breaks in through that door, giving you a way through.
Above Goldenrod city,walk into the room where thay tell you about the bug contests and go through the far left door. et
It,s in eterna city
The black tall building with a shop door
In case in goldenrod city take the underground path. There will be a door. Get the key from the rocket executive in radio tower. In case of lavender town we can't go underground.
ok well if you going north from goldenrod city , when you get in the building at the end to leave the city , just follow the path until you get to anothwer building . if you were to go straight through , you would end up in the national park , but when your inside , take a left and there will be a door . go through the door and youll end up at the pokeathlon dome.
Enter the vault through the ceiling, get the information from the first spy, and then leave through the double door.