The best answer seems to be the first one: The chateau is situated in a remote area.
According to the description, the chateau is located in an area difficult to access. It's at the top of a bluff - bluff is a steep cliff or bank by the sea or a river - and three sides of the bluff sound impenetrable, the walls reaching the sea in an abrupt descent.
Even though the chateau is described as palatial, and probably belongs or used to belong to a rich person, from this description alone it cannot be inferred that it was a general who owned it.