Archbishop Marsh’s Library
The library's founder, the Archbishop Narcissus Marsh, believed that everyone should have access to books on medicine, law, science, travel, navigation, mathematics, music, classical literature, and, of course, theology. He hired a 19-year-old niece to be his housekeeper, but she stole out of her room one night to be with the vicar of Castleknock in a tavern, and was "bedded there with him-Lord consider my affliction," Marsh wrote. She later regretted her actions and, it is said, wrote her uncle a letter, which she slipped between the pages of a book that he never could find. His ghost haunts the library searching through the books for that letter.