It is in the Lower Cave of Mt. Mortar. You will need Rock Climb to get it.
Inside Mt. Mortar
Chat with our AI personalities
at the cerulean cave
You can find it in Pokemon Platinum, Pokemon Crystal, Pokemon HeartGold, and Pokemon SoulSilver.
Find and then catch
You can only find Skarmory in the Pokemon SoulSilver version.
Cynthia is not the champion in the johto region in Pokemon heartgold,you can't find her in it, but she is the champion in Pokemon pearl,diamond, and platinum versin and that is the sinnoh region.