From A Wiki of Ice and Fire
Acorn Hall has stone curtain walls and a large oak keep. The keep has a forge which has not been used for a considerable amount of time.
A Storm of Swords
Arya Stark and the brotherhood without banners including Tom Sevenstrings, who had once been Lady Ravella Smallwood's lover, travel through Acorn Hall where Lady Smallwood welcomes them, opening the keep's gates for them to rest there. Ravella notices Arya's dirtiness and forces her to take a shower and clean herself, though not knowing who Arya really is . Afterwards, Ravella chats with Arya discussing tastes and the courtesies of a lady after discovering that Arya is highborn.
The brotherhood feast with Arya and Lady Smallwood in the keep's hall. They ask the lady if she has word of Lord Beric Dondarrion and soon everyone begins chatting with each other. Ravella mentions that Ser Jaime Lannister escaped Riverrun and some Karstark men had gone through Acorn Hall looking for Jaime.
After the feast, Gendry and Arya go to the forge where they talk about Thoros of Myr and Gendry compliments Arya for her new, more highborn looks. The day afterwards, Lady Smallwood makes Arya take another bath before parting ways with the little lady and the brotherhood without banners, who proceed with their journey to find Lord Beric.
References and notes