The Church of San Eustaquio is in the Mudejar style and is located at the highest point of the old town of Sanlúcar la Mayor. According to tradition, the church of San Eustaquio was built on the ruins of an old Roman temple dedicated to the sun.
The Church of San Eustaquio consists of three naves separated by pointed arches. Inside we can find a Baroque style main altarpiece (18th century). On the left we can see a Rococo altarpiece with an image of the Virgen de los Remedios and another of the Cristo de la Salud, both 16th century. In the right lateral nave are the 16th-century sculptures of La Concepción and San José, and in the chapel of the Tabernacle is the Virgen de Fuentes Claras (15th century).
It also contains images, paintings and altarpieces from the 16th, 17th, 18th and 19th centuries. Regarding the invocation of San Eustaquio, it is known that in 1570 he was already considered the patron saint of the town, but it was during the time of the Count-Duke of Olivares when the fervour for the Christian martyr was renewed since, upon his return from his stay in Rome as the ambassador of Enrique de Guzmán, he brought numerous relics to Spain, including the relics of San Eustaquio, which were donated to different institutions such as the cathedral of Seville or the Hospital de los Venerables.
Thus, it could be said that it was because of the close ties between the house of Olivares and Sanlúcar la Mayor that this devotion to San Eustaquio was reinforced. So much so that a wooden carving of the saint, dating from the 16th and 17th centuries and thought to be the work of Martínez Montañés, was commissioned.