Mexico (Spanish: México),[a][b] officially the United Mexican States,[c] is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatemala, Belize, and the Caribbean Sea; and to the east by the Gulf of Mexico.[12] Mexico covers 1,972,550 km2 (761,610 sq mi),[13] making it the world's 13th-largest country by area; with a population of over 126 million, it is the 10th-most-populous country and has the most Spanishspeakers.[5] Mexico is organized as a federal republic comprising 31 states and Mexico City, its capital. Other major urban areas include Monterrey, Guadalajara, Puebla, Toluca, Tijuana, Ciudad Juárez, and León.[14] Human presence in Pre-Columbian Mexico goes back to 8,000 BCE and it went to become one of the world's six cradles of civilization. In particular, the Mesoamerican region was home to many intertwined civilizations, including the Olmec, Maya, Zapotec, Teotihuacan, and Purepecha. Last were the Aztecs, who dominated the region in the century before European contact. In 1521, the Spanish Empire and its indigenous allies conquered the Aztec Empire from its capital Tenochtitlan (now Mexico City), establishing the colony of New Spain.[15]