While not technically in Monterotondo Marittimo, this church is in nearby Frassine and is too beautiful not to mention. It is considered one of the most important shrines in the Maremma and was finished during the 15th century. The shrine is tied to the Fraxinus excelsior, a tree that was revered by the ancient Nordics and was burned in the Maremman countryside to ward off evil spirits.
The Santuario del Frassino is home to many beautiful paintings and relics, not to mentioned surrounded by a picturesque countryside that is perfect for an afternoon walk...but that's not what draws visitors to this church.
Legend has it that the statue was found by a farmer who followed his ox into the woods one day. The farmer found his ox kneeling in front of an ash tree where monks had hidden the statue of the Madonna. After hearing the legend, local 15th century followers decided that the Madonna had chosen this site as her trono di misericordia and thus built a church in her name.