Lake Texcoco in the context of "Mexica"

Tenochtitlan, also known as Mexico-Tenochtitlan, was a large Mexican altepetl in what is now the historic center of Mexico City. The exact date of the founding of the city is unclear, but the date 13 March 1325 was chosen in 1925 to celebrate the 600th anniversary of the city. The city was built on an island in what was then Lake Texcoco in the Valley of Mexico. The city was the capital of the expanding Aztec Empire in the 15th century until it was captured by the Tlaxcaltec and the Spanish in 1521.

At its peak, it was the largest city in the pre-Columbian Americas. It subsequently became a cabecera of the Viceroyalty of New Spain. Today, the ruins of Tenochtitlan are in the historic center of the Mexican capital. The World Heritage Site of Xochimilco contains what remains of the geography (water, boats, floating gardens) of the Mexica capital.

The Aztecs (/ˈæztɛks/ AZ-teks) were a Mesoamerican civilization that flourished in central Mexico from 1300 to 1521. The Aztec people included different ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language. Aztec culture was organized into city-states (altepetl), some of which joined to form alliances, political confederations, or empires. The Aztec Empire was a confederation of three city-states established in 1427: Tenochtitlan (the capital city of the Mexica or Tenochca), Tetzcoco, and Tlacopan, previously part of the Tepanec empire, whose dominant power was Azcapotzalco. Although the term Aztecs is often narrowly restricted to the Mexica of Tenochtitlan, it is also broadly used to refer to Nahua polities or peoples of central Mexico in the prehispanic era, as well as the Spanish colonial era (1521–1821).

Most ethnic groups of central Mexico in the post-classic period shared essential cultural traits of Mesoamerica. The culture of central Mexico includes maize cultivation, the social division between nobility (pipiltin) and commoners (macehualtin), a pantheon, and the calendric system. Particular to the Mexica of Tenochtitlan was the patron god Huitzilopochtli, twin pyramids, and the ceramic styles known as Aztec I to IV. The Mexica were late-comers to the Valley of Mexico, and founded the city-state of Tenochtitlan on unpromising islets in Lake Texcoco, later becoming the dominant power of the Aztec Triple Alliance or Aztec Empire which conquered other city-states throughout Mesoamerica. It originated in 1427 as an alliance between the city-states Tenochtitlan, Texcoco, and Tlacopan to defeat the Tepanec state of Azcapotzalco, which had previously dominated the Basin of Mexico. Soon Texcoco and Tlacopan were relegated to junior partnership in the alliance, with Tenochtitlan the dominant power. The empire extended its reach by a combination of trade and military conquest. It was never a true territorial empire controlling territory by large military garrisons in conquered provinces but rather dominated its client city-states primarily by installing friendly rulers in conquered territories, constructing marriage alliances between the ruling dynasties, and extending an imperial ideology to its client city-states. Client city-states paid taxes, not tribute to the Aztec emperor, the Huey Tlatoani, in an economic strategy limiting communication and trade between outlying polities, making them dependent on the imperial center for the acquisition of luxury goods. The political clout of the empire reached far south into Mesoamerica conquering polities as far south as Chiapas and Guatemala and spanning Mesoamerica from the Pacific to the Atlantic oceans.

The Valley of Mexico (Spanish: Valle de México; Nahuatl languages: Anahuac, lit. 'Land Between the Waters'), sometimes also called Basin of Mexico, is a highlands plateau in central Mexico. Surrounded by mountains and volcanoes, the Valley of Mexico was a centre for several pre-Columbian civilizations including Teotihuacan, the Toltec, and the Aztec Empire. The valley used to contain five interconnected lakes called Lake Zumpango, Lake Xaltocan (Nahuatl languages: Xāltocān), Lake Xochimilco, Lake Chalco and the largest, Lake Texcoco, covering about 1,500 square kilometers (580 sq mi) of the valley floor. When the Spaniards arrived in the Valley of Mexico, it had one of the highest population concentrations in the world with about one million people. After the conquest of the Aztec Empire, the Spaniards rebuilt the largest and most dominant city, Mēxihco Tenōchtitlan, renaming it Ciudad de México (Mexico City) and over time began to drain the lakes' waters to control flooding.

The Valley of Mexico is located in the Trans-Mexican Volcanic Belt. The valley contains most of the Mexico City metropolitan area, as well as parts of the State of Mexico, Hidalgo, Tlaxcala, and Puebla. The Basin of Mexico covers approximately 9,600 km (3,700 sq mi) in the NNE-SSW direction with length to width dimensions of approximately 125 km (78 miles) to 75 km (47 miles) The Valley of Mexico can be subdivided into four basins, but the largest and most-studied is the area that contains Mexico City. This section of the valley in particular is colloquially referred to as the "Valley of Mexico".The valley has a minimum elevation of 2,200 meters (7,200 ft) above sea level and is surrounded by mountains and volcanoes that reach elevations of over 5,000 meters (16,000 ft). It is an enclosed valley with no natural outlet for water to flow to the sea although there is a gap to the north where there is a high mesa but no high mountain peaks. Within this vulnerable watershed all the native fishes were extinct by the end of the 20th century. Hydrologically, the valley has three features. The first feature is the lakebeds of five now-extinct lakes, which are located in the southernmost and largest of the four sub-basins. The other two features are piedmont, and the mountainsides that collect the precipitation that eventually flows to the lake area. These last two are found in all four of the sub-basins of the valley. Today, the Valley drains through a series of artificial canals to the Tula River, and eventually the Páruco River and the Gulf of Mexico. Seismic activity is frequent here, and the valley is an earthquake-prone zone.

Tetzcoco (Classical Nahuatl: Tetzco(h)co pronounced [tetsˈkoʔko], Otomi: Antamäwädehe) was a major Acolhua altepetl (city-state) in the central Mexican plateau region of Mesoamerica during the Late Postclassic period of pre-Columbian Mesoamerican chronology. It was situated on the eastern bank of Lake Texcoco in the Valley of Mexico, to the northeast of the Aztec capital, Tenochtitlan. The site of pre-Columbian Tetzcoco is now subsumed by the modern Mexican municipio of Texcoco and its major settlement, the city formally known as Texcoco de Mora. It also lies within the greater metropolitan area of Mexico City.

Pre-Columbian Tetzcoco is most noted for its membership in the Aztec Triple Alliance. At the time of the Spanish conquest of the Aztec Empire, it was one of the largest and most prestigious cities in central Mexico, second only to the Aztec capital, Tenochtitlan. A survey of Mesoamerican cities estimated that pre-conquest Tetzcoco had a population of 24,000+ and occupied an area of 450 hectares.

Tlacopan, also called Tacuba, (Classical Nahuatl: Tlacōpan, [t͡ɬaˈkóːpan̥]) was a Tepanec / Mexica altepetl on the western shore of Lake Texcoco. The site is today the neighborhood of Tacuba, in Mexico City.

Azcapotzalco was a pre-Columbian Nahua altepetl (state), capital of the Tepanec empire, in the Valley of Mexico, on the western shore of Lake Texcoco.

The name Azcapotzalco means "at the anthill" in Nahuatl. Its inhabitants were called Azcapotzalca.