Pokémon Heart Gold and Soul Silver

[Dragoon]

Maybe I'm wrong (haven't really played Pokemon since generation 2 when was helping a busmate to catch and level up night time only Pokemon, otherwise I was pretty much a Generation 1 player) but is only the overworld 3D, or are both overworld and buildings 3D too?

Overworld, some types of insides(caves, forests, some buildings) are 3D, Gate houses and normal building insides are not 3D.