Spanish conquistadors first reached Tenochtitlan in 1519. Hernán Cortés and his Spanish forces entered the Mexica capital on 8 November 1519, after traveling inland from the Gulf Coast and forming alliances with Indigenous enemies of the Aztec Empire.
Tenochtitlan stood on an island in Lake Texcoco and was connected to the mainland by causeways. It was the political and religious center of the Mexica-led empire, with monumental temples, palaces, markets, and canals. Spanish observers were astonished by its size and organization.
A common mix-up is 1521, the year Tenochtitlan finally fell after a long siege involving Cortés, Spanish troops, and thousands of Indigenous allies. Thus, 1519 marks the first Spanish arrival in the city, while 1521 marks its conquest and destruction. The encounter began a three-year conflict that transformed the history of central Mexico.