The site of the castle of Monterotondo Marittimo is mentioned in Lucchese documentation from the 8th century onward, but it is not until 1070 that we have a first mention of the castle falling within the rule of the Aldobrandeschi family. The castle has always been included in the Volterra jurisdiction and only in the 14th century was it controlled by Massa Marittima.

The Rocca degli Alberti represents the oldest part of the entire historic center of Monterotondo Marittimo. Excavations, conducted by the University ofSiena, have brought to light evidence attributable to the 9th and 10th centuries AD, a period that most likely coincides with the first occupation of the area. The most reliable hypothesis, at least for this first phase, is that the settlement had been promoted by a strong private initiative, that had sought to create a management center where the resources gathered in the area could flow. Once at the Rocca, the tour route, equipped with panels, allows those who intend to visit its ruins to retrace the history of this important fortification.
As well as the Fortress of Monterotondo, the church of San Lorenzo is also worth mentioning. The architectural complex we see today dates back to the 16th century. In fact, according to some archival documents it seems that there was an older church in the same area. Unfortunately, no reliable clues about its possible location have yet emerged. San Lorenzo houses two relevant paintings inside: a Madonna and Child and a depiction of the Esequies of a Saint. Of the latter pictorial work, the setting halfway between Neoclassical and Romanesque is striking.
The municipal territory of Monterotondo Marittimo is rich in places to visit. For those who love walking and sacred sites, the church of Santa Croce, the oratory of the Madonna di Montenero, and the sanctuary of the Madonna di Frassine are worth a visit. For all those who are more inclined to nature trails, however, a stop at the Biancane Park is recommended. The trail starting from Via dei Lagoni Boraciferi winds through geothermal manifestations typical of the area (soffioni, boraciferous lakes, etc.) to the geothermal power plants. Panels placed on the various paths illustrate to visitors what they will observe.