The Quattro Comuni provincial road crosses the Sterza torrent several times, one of the main tributaries of the Cecina and one of the most uncontaminated and interesting torrents for the natural environments of the upper course. In the past, the Sterza Valley was also very important for mining, as can be seen from the remains of the old 19th-century mining railway that ran along this stretch of the valley as far as Casino di Terra.