Pokémon HeartGold and SoulSilver/Dragon's Den

In the Dragon's Den, after you defeat the eigth Gym Leader, Claire, you will enter and find that you will be fighting three battles: Dragonair twice and some others. Then you will enter a building—to get there you need whirlpool. Once you get inside, you will be asked several questions and then you will see Claire walk in after you have passed. She will give you the eigth Gym Badge. Then you will leave.