Also known as the Pieve (Parish Church), it has always played a key role in the history and social life of the State. The building dates back to July 24, 1825 and was ordained by the Council of the Sixty. The works began the following year, with the laying of the foundation stone by Antonio Begni from Montecerignone, bishop of Montefeltro, and ended in 1838, under the supervision of the architect Antonio Serra from Bologna, to whom we owe the building project. The religious importance of the Basilica is also evidenced by the visit of Pope John Paul II on 29 August 1982 and of Benedict XVI, on 19 June, 2011, during his pastoral visit to the diocese of San Marino - Montefeltro. At first glance you can see the building is in Neoclassical style, with the main façade preceded by a staircase upon which are eight Corinthian columns. The interior is divided into three naves by Corinthian columns and there are several plaster statues depicting the Twelve Apostles and the Redeemer. They were all made by the school of the sculptor Adamo Tadolini, who also designed the Statue of Saint Marinus placed behind the altar. Other works worthy of interest are the four Cardinal Virtues, at the corners of the nave, the throne of the Captains Regent, dating from the seventeenth century and the painting called "Noli Me Tangere" by Elisabetta Sirani, representing the risen Christ. Under the main altar, kept in a small urn, are the Sacred Bones of Saint Marinus, Founder of the Republic.
