The 16th-century San Ildefonso Church is the seat of the Confraternity of the Transfixion and Our Lady of Solitude.
The building has an entrance at the west front and another on the Epistle aisle, both with semi-circular arches between pilasters. The main entrance is crowned by a pediment with pinnacles crowned by an oculus.
The church consists of a nave with a polygonal apse in which the main altar is situated, presided over by the image of Our Lady of Mercy, and two aisles separated from the nave by rows of pillars with attached pilasters.
Adjacent to the left aisle is a square building with the Chapel of Our Lady of Sorrows. The chapel, now used by the Confraternity of Our Lady of El Rocío, was formerly the baptistery. Opposite the chapel is the staircase leading to the choir loft and, further up, a small roof terrace behind the bell gable. Finally, next to the sanctuary is the chapel of Our Lady of the Rosary and the Blessed Sacrament.
The church is dedicated to Saint Ildephonsus, the patron saint of Mairena del Aljarafe. Although the building was initially built in the Mudéjar style, it was gradually modified over time. The temple was originally a chapel of a church in Palomares del Río. It was not until 1640-1674 when the building was divided into a nave and two aisles. Around that time, the bell tower with three bells was added to the church, as were its south and west doors. The altarpiece with the Sacred Heart of Jesus dates from 1612.