When Hernán Cortés and his army reached Tenochtitlan, in early November 1519, the capital of the Aztec Empire, gleaming like a jewel on an island in Lake Texcoco in the Valley of Mexico, had a population of nearly three hundred thousand. The political and religious heart of the city was organised around a large ritual wall dominated by an impressive pyramid dedicated to the god of rain and fertility (Tlaloc) and to the ancestral god of war and the sun (Huitzilopochtli). From this centre, the Aztecs and their partners in the Triple Alliance (Texcoco, Tlacopan) controlled a large part of Mesoamerica.