The Plaza occupies roughly the same site as the main square of the pre-Columbian town of Tlatelolco, Tenochtitlán's great rival until 1473, when the Aztecs captured the town and killed its ruler by hurling him from the principal pyramid. However, Tlatelolco still remained the most important trading town in the region with a market which, according to the accounts of the conquistadors, was visited by 60,000 people every day. During the siege of Tenochtitlán by the Spaniards in 1521 Tlatelolco was the scene of the last desperate stand by the Aztecs. This event is remembered by means of a memorial tablet bearing the words "On 13 August 1521 Tlatelolco, so heroically defended by Cuauhtémoc, finally fell into the hands of Hernán Cortés. It was neither a triumph nor a defeat; it was the painful moment of birth of the Mexico of today, of a race of mestizos".
The square was designed by Mario Pani and completed in 1964. It takes its name from the fascinating juxtaposition of buildings from three different periods - Aztec pyramids and temples, a Spanish conventual church and modern tower blocks. In 1968 the police fired on a crowd which was demonstrating in the square and, according to unofficial estimates, killed some 250 people. In 1985 and 1986 it was covered with tents to provide shelter for the many who had been rendered homeless by the earthquake.</blockquote>