Saint Patrick's Basilica - Credit: Wikimedia Commons
St Patrick's Purgatory is an ancient pilgrimage site on Station Island in Lough Derg, County Donegal, Ireland. According to legend, the site dates from the fifth century, when Christ showed Saint Patrick a cave, sometimes referred to as a pit or a well, on Station Island that was an entrance to Purgatory.Bieler, Ludwig. "St. Patrick's Purgatory: Contributions towards an Historical Topography.” The Irish Ecclesiastical Record 93 (1960): 137–44. Read more on Wikipedia
Source: en.wikipedia.org