High Quality Content by WIKIPEDIA articles! Val di Merse is one of the regions of the province of Siena, in Tuscany. It is located on the border with the Upper Maremma and it is renowned for its unspoilt nature. The territory comprises the area between the rivers Farma and Merse and it is covered in woods which hide medieval hamlets and castles. It is an area rich in waters known for their healing powers, such as the hot springs of Bagni di Petriolo.