The Parish of Santiago is a Gothic-Mudejar temple erected at the beginning of the 16th century, although there are documents that suggest dating from the first half of the 15th century. It was built taking advantage of the stone from the old Castle, which by royal mandate was demolished in 1508.
It has become a pantheon of some of the most relevant characters in the town, such as the Alvear and Garnelo families. It has an imposing architecture of three naves with numerous chapels in the lateral naves of which stand out on one side the Chapel of Baptism in which San Francisco Solano was baptized. On the other hand, it houses one of the jewels of heritage not only from Montillano but from Spain, the Mexican carving of Cristo de Zacatecas made from vegetable fibers of corn and glued cane, as well as the series of the apostolate of José Garnelo y Alda and the Miracle of the would, which today shine in all its splendor thanks to the latest restorations and new lighting.