Hy-Brasil
"The enchanted circular Atlantic island that persisted on European nautical charts for over 500 years"
First appearing on Angelino Dulcert's 1325 portolan chart as a perfectly circular island divided by a central river, Hy-Brasil was said in Celtic folklore to be cloaked in perpetual fog, revealing itself to mortals only once every seven years.
Cartographic Origin Story
Stemming from Gaelic mythology (*Uí Breasail* meaning 'Clan of Breasal'), it was repeatedly sought by Bristol explorers—including John Cabot in the 1490s—who claimed to have sighted land in its general vicinity.
Illustrates how cultural mythological motifs become reified into hard navigational cartography through unverified copying across generations of chartmakers.
Scientific Disproof or Geological Fate
Hydrographic surveys by the British Admiralty throughout the 19th century systematically sounded the Porcupine Bank, finding shallow submarine banks (145m deep) but zero dry land, finally purging it from official charts in 1865.