1561 celestial phenomenon over Nuremberg
In April 1561, a broadsheet by Hans Glaser described a mass sighting of celestial phenomena or unidentified flying objects (UFO) above Nuremberg (then a Free Imperial City of the Holy Roman Empire). Ufologists have speculated that contemporary observers may have witnessed extraterrestrial spacecraft.
Source: Wikipedia — 1561 celestial phenomenon over Nuremberg (CC BY-SA 4.0)