You normally have to defeat a Pokemon to get a key or you sometimes find it lying around on the floor.
Keys are found randomly around the floors of Solar Cave and Western Cave in Pokemon Mystery Dungeon.
If you are referring to the Key Card for the Silph Co. building that Team Rocket has taken over in Saffron City, it is on the 5th Floor. Go all the way down and there should be a Rocket member next to a teleporter. Step on the teleporter and it will teleport you to a room with a scientist. Go back on the teleporter and travel downwards, and then make a right and you will see the key card.
Um, i think you use the thing on your poketch and go on the one if you touch it it beeps and a circle starts small and goes big and disssapears then it should be close to where that lady is i think that's what you do anyway.............
In the abandoned mansion on cinnabar island it's at the top left you search throughout the building untill u find a poke ball and it will contain a key then go back to the gym with a level 40. + fire or water Pokemon and hope for the best
If you mean Klefki, it can be caught at Route 15, Route 16 and inside the Lost Hotel.
If you have enough Friend Codes registered on your Nintendo 3DS, you may also find a Klefki in the Friend Safari located in Kiloude City. Each friend has a Pokémon type associated with him/her so you just need to visit a Steel-type safari but please keep in mind that each safari can only have two to three unchangeable Pokémon.
at the berry guy's house go down and you'll see a guy under the grass, he'll give you the odd keystone, which you can use on the stone tower and get (somehow, look it up)spiritomb
They can be found in harder dungeons, in the deepest floors randomly.
There is no key, you must have a Pokemon with at least ten ribbons.
The key is laying on a table in the deepest part of the Pokemon mansion. You can find it lying on the table and it's used for opening the gym.
go on Pokemon Platinum Walkthrough you'll might get the idea.
You will need to work your way to the basement in the Pokemon Mansion, you will then find the Key.
The tanoby chambers are ruins where a certain Pokemon is lurking to find that Pokemon you must first solve the boulder puzzle in tanoby key once you do that you can find that Pokemon in the chambers.
There is no key, you must have a Pokemon with at least ten ribbons.
You will find the key to the Gym of Cinnabar Island, From the Pokemon Mansion that is on the same island.
The Special Key is a key item in Pokemon Diamond. You can find this item in a warehouse in Veilstone City.
In the house you jerk!
bgfhbfr
you find it in deep inside Pokemon mansion i think
you find the basement key in the underground path
You find a cave, go into it, then find a legendary pokemon, catch that pokemon, and then leave the cave.
u can find it in Pokemon mansion.
The key is laying on a table in the deepest part of the Pokemon mansion. You can find it lying on the table and it's used for opening the gym.
you find it in the galactic HQ
you can't.