Grotte di Castro within its medieval walls hides many places of great historical value, one of the most interesting places to see is the sanctuary dedicated to Maria Santissima del Suffragio. Built in 1625 on a previous 8th-10th century church which was destroyed by the Lombard invasions, the sanctuary is one of the main religious buildings in the town. Originally the church was under the control of the bishop of Orvieto and in 1378 it passed to the diocese of Montefiascone. In 1462 this sacred place of worship was honored by the presence of Pope Pius II who gave the church a precious reliquary: a cross and a chalice of immense value and granted the grace to seven souls on the occasion of the feast of St. John the Baptist if they had contributed to its maintenance. Unfortunately there is not much information on the original structure of this church, what we do know is that it has undergone countless transformations over the years that have given the appearance of the current one. According to some scholars, it took 47 years to build the Sanctuary of Maria del Suffragio in Grotte di Castro and only in 1672 was the ovoid dome built by Andrea Selvi and decorated by Luigi Fontana between 1886 and 1888.
The cult of the Madonna del Suffragio is to be attributed to a certain Capuchin friar known by the name of Father Angelo di Ronciglione who, in the course of the 17th century, placed the image of the Virgin still preserved today on the high altar. This church is so important not only from a historical and architectural point of view, but also and above all from a cultural point of view that every year in Grotte di Castro on 8 September the saint is celebrated with a solemn procession.