It's worth the effort delving into the history of its Christ of Agony.
Our Lord of May.
It was the first church founded by the Augustinians on arriving in Chile and that is why, although its official name was always Nuestra Señora de Gracia (Our Lady of Grace), for centuries it has been known as La Iglesia de San Agustín (the Church of St. Agustin). The church was begun in 1609 and nearly forty years later the miracle took place. The image of the Christ of Agony was housed in it (also known as the Lord of May), one of the most significant sculptures of its time, when the tragic earthquake of 13th May 1647 took place. The church, like so many other buildings was destroyed, except, miraculously, the image of Christ fully intact, although the crown of thorns had fallen onto his throat. This story increased devotion to the sculpture, the first made in Chile, by the Peruvian Friar Pedro de Figueroa, in 1612. Since then, every 13th May the sculpture is paraded throughout the city, hence the nickname, the Lord of May. Besides this well known stature, the Church of Saint Augustine is pictorially very interesting for its painted dome, the altar to St. Rita and the collections of works by Chilean artists it keeps.