You probably refer to the one you can use to display items. You have to start the quest "beauty and the beast" by looking for Hog on Friday in his tavern (he won't be there and Miles will notice that) and then ask Nancy about Hog and then enter the basement and read the document on the bed.

After that locate the hedge maze (exit the village to the north and head northeast) and find the mansion to the north on Friday or you won't have access to the building. After that finish the quest and the mansion is yours. The attic is at the top but needs  to be renovated.