Csíksomlyó became a pilgrimage site in 1567, when Hungarian king John II Sigismund Zápolya wanted to convert the Székely population of the upper Csík to Protestantism. The Székelys refused to abandon the Catholic faith and resisted. A battle took place on a nearby field, on Saturday before Pentecost 1567, from which the Székelys emerged victorious. The monks saw this as a sign of the care of Virgin Mary, and since then, this event has been commemorated by a pilgrimage when the believers gather on Pentecost every year. Beside its religious importance, the pilgrimage has also become a community event demonstrating spiritual unity of Hungarian people living in and outside the historical region of Transylvania. In the 1990s the church and the surrounding region could no longer accommodate the hundreds of thousands pilgrims. In 1993, a new altar was built at the mountain side and since then the celebration of the Eucharist have been taking place outdoors.