The Knock shrine encompasses five churches and a museum in the town centre. People of many faiths pray at the modern chapel enclosing a scene of the apparition carved from snow-white marble. A segment of stone from the original (and long-gone) church mounted on the outside wall (on your right as you're facing the scene of the apparition) has been rubbed smooth by the hands and lips of the faithful.
The story that led to Knock's development goes thus: on the evening of 21 August 1879, in drenching rain, two young Knock women were startled by a vision of Mary, Joseph, St John the Evangelist and a sacrificial lamb upon an altar, freeze-framed in dazzling white light against the southern gable of the parish church. They were soon joined by 13 more villagers, all gazing at the heavenly apparition for around two hours as the daylight faded. A Church investigation confirmed it as a bona fide miracle, and a sudden rush of other Vatican-approved miracles followed as the sick and disabled claimed amazing recoveries upon visiting the spot.
Besides the sacred chapel, there is the vast 1970s Basilica of Our Lady, Queen of Ireland, which can accommodate more than 10,000 people.