Siege of Concepcion
1564 CE.
Shown on the map at -36.833°, -73.050°.
During the siege of Concepcion of the Arauco War, 20,000 warriors of the army of the Mapuche laid siege to the Spanish garrison and civil population in the fortress of Concepcion, Chile.
Text from the Wikipedia article Siege of Concepción, licensed CC BY-SA 4.0.