Early Mexicans refers to two major civilizations that existed in Mexico before the Spanish conquest: the Aztecs and the Olmecs. The Aztecs were a Mesoamerican culture that flourished in central Mexico in the 14th to 16th centuries. They built a powerful empire and developed a complex society, with a highly developed religious system. The Olmecs were an ancient civilization that flourished in the tropical lowlands of south-central Mexico from about 1200 BCE to about 400 BCE. They are considered to be the first major civilization in Mexico and are known for their large monuments and sculptures.