Where do you catch articuno in heartgold?

You can't catch Articuno in Pokémon HeartGold. Articuno is only available in the Johto region games (Gold, Silver, Crystal) and in Pokémon SoulSilver.

Here's why:

* Articuno is a legendary Pokémon: Legendary Pokémon are generally not available in every generation of games.

* HeartGold and SoulSilver are remakes: They mostly follow the same story and Pokémon availability as the original Gold and Silver games.

If you want to catch Articuno, you'll need to play Pokémon SoulSilver.