Rupes Nigra (The Black Rock)
"Mercator's 33-mile magnetic black lodestone mountain at the center of the Arctic whirlpool"
On his famous 1569 world map and 1595 polar map, Gerardus Mercator placed an immense 33-mile-wide magnetic black rock (*Rupes Nigra*) at the exact North Pole, surrounded by four giant inward-flowing rivers plunging into an abyssal central whirlpool (*The Navel of the Earth*).
Cartographic Origin Story
Based on the lost 14th-century travelogue *Inventio Fortunata*, which attempted to explain why compass needles point north by positing an actual magnetic mountain.
A classic theoretical physical model designed to provide a physical substrate for invisible geomagnetism.
Scientific Disproof or Geological Fate
Polar expeditions by Willem Barentsz (1596) and William Baffin (1616) disproved solid land, leading cartographers to replace the rock with open frozen ocean.