The original building of the convent dates back to the period between 1481 and 1496. Since 2009, it has been the Municipal Hall. After 1861, the church and convent of Saint Mark were declared property of the Municipality. The church was given in custody to an Augustine priest and a lay person until 1910, when the Augustines left Montecassiano for good. Noteworthy are the fresco paintings from the 19th century on the ceiling of the southeast hall of the complex, representing the Allegories of the Arts, and in the central medallion, Diana the huntress. The adjacent room, rather large, has a painting on the ceiling of the municipal coat of arms.