Pokémon HeartGold and SoulSilver/Dragon's Den

In the Dragon's Den, after you defeat the eighth Gym Leader, Clair, 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 Clair walk in after you have passed. She will give you the eighth Gym Badge. Then you will leave. If you answer all five questions correctly, you will also receive a Dratini with ExtremeSpeed. After getting the National Pokedex, come back here for a Double Battle with Clair and Lance, and a second time after winning the Double Battle to get Clair's phone number.