Howling Forest
From Bulbapedia, the community-driven Pokémon encyclopedia.
The first main rescue in the Howling Forest is to punish the bad mankey.
This leads to the construction of your new team base which looks like your head. Anyway this dungeon has ten floors.On the ninth or tenth you will find chestnuts (payment for the mankey gang to work on your base.You'll need about three) and other
useful items.