Hy-Brasil

The phantom island on six centuries of serious charts, visible one day in seven — and named, note the UFO files, in the Rendlesham binary.

Hy-Brasil appears on portolan charts from 1325 (Dalorto) through the 1800s — a documented cartographic persistence of a phantom island west of Ireland, likely cloud banks, Porcupine Bank shoals, or copied error. Its conspiracy afterlife comes from the Rendlesham binary: Penniston's 2010 decoding of his claimed 1980 download includes Hy-Brasil coordinates (52.0942532N 13.131269W) — which is documented as his claim, thirty years after the event, with the coordinates' provenance debated even among Rendlesham researchers. The node links medieval cartography's ghost to the modern file that adopted it.