On the isolated island of Staffa, next to Iona in Scotland, stands one of the natural wonders of the world. Fingal's Cavean extraordinary Cathedral-like space, with sides and roof of hexagonal basaltic columns, with a floor made of the ocean, which is constantly making musical sounds as the tides ebb and flow. This cave has been a source of mystery, spiritual insight, and artistic inspiration for centuries. To understand Fingal, and his importance in Celtic culture, we must understand both the poems of Ossian, collected by the 18th century poet James Macpherson, and the development of Celtic Christianity from the druids and bards of long ago. Paul and Joan Allen describe the history and importance of Fingal's Cave and The Poems of Ossian to contemporary culture today, and show why they have influenced many diverse figures including Mendelssohn, Jefferson, Napoleon, Turner, and others.