What is the fine-grained topic of the following text: Nestled in the Valnerina, (Valley of the Nera) between the mountains of Sant'Angelo and Gabbio lies the Umbrian village of Ferentillo, above the seventy square kilometre hamlet are the castles of Precetto and Matterella, facing each other as if in a defiant, permanent stand off as they look down upon the village. Only return the topic.
The Umbrian village of Ferentillo and its surrounding landmarks.