The parish church at the heart of the upper village dates from the 12th to 15th centuries and is the oldest surviving structure in Mailly-le-Château. The nave walls retain Romanesque stonework, while the choir and side chapels were added in the Gothic period. The exterior is particularly striking from the cliff-side path: the square tower rises above the roofline against a backdrop of the Yonne valley. The interior is plain and unrestored, which suits it well.