Aztec calendar, centred around a Sun with four winds. This 52-year cycle (xiuhmolpilli) is divided into four colour-coded sections (clockwise from upper left): acatl (reed, green, east); tochtli (rabbit, blue, south); calli (house, yellow, north); and tecpatl (flint, red, north). Green represents the paradise of Tamoanchan; red represents sacrifice. The Aztec Empire (ruled by the Mexica) was an alliance of three city states that ruled in central Mexico from 1428 until their defeat by Spanish conquistadors in 1521. Artwork from a 19th-century copy of a 16th-century post-conquest codex and history of the Aztecs by Jesuit missionary Juan de Tovar.