The Romanesque nave is the oldest part of the church. The choir has a stone vault on a ribbed vault, divided into two bays, in the upper part of the high altar. The stained glass window is from the beginning of the 16th century, it represents the marriage, in 1505, of Mary of Melun with John of Bruges with, behind the two characters, Saint John and the Virgin. The Gothic-style sink dates from the 16th century, with a main shelf carved out of two round basins. On the sides are two columns with small capitals carved. Period and Romanesque styles: XIIIth XIXth XVIIth Gothic: XIIth In 1625, addition of a side nave. In the 19th century, construction of the chapel of the castle and the sacristy, then modification of the choir. In 1505 Jean de Bruges had the choir rebuilt for his wedding. History and important dates: The Church of Our Lady of the Assumption is from various eras. The church was built in the 15th and 16th centuries. Originally dependent on the bishopric of Chartres, the parish of Montmirail was not attached to the bishopric of Le Mans until 1801. Notable elements: blessing(s), altarpiece(s), choir, baptismal font, pulpit(s), nave(s), stained glass windows, capitals, good state of conservation.