The Dilemma: You’re pretty sure both these ancient civilizations were located north of Antarctica and south of Dallas—but that’s about all you know.

People You Can Impress: It’s not so much a matter of impressing people as it is not embarrassing yourself when chatting up armchair historians.

The Quick Trick: The dominant ethnic group in the Aztec empire were the Mexica (pron. meh-SHEE-kuh), hence Mexico. The Inca empire was centered in what is today Peru.

The Explanation:
It’s easy to confuse your Aztecs with your Incans because they have a great deal in common: Both empires reached their peaks in the early 16th century, both made huge technological and scientific discoveries, both dabbled in the delicate art of human sacrifice, and both suffered mightily at the hands of Spanish conquistadors.

As for differences, though, the easiest distinction is geography. The Inca empire controlled parts of modern-day Chile, Peru, Argentina, Ecuador, Bolivia, and Colombia. The Aztecs, meanwhile, set up camp more than 1,000 miles to the north. To protect themselves from invaders, the Aztecs built their capital city, Tenochtitlán, on a large island in the middle of Lake Texcoco. These days, Mexico City stands upon the ruins of Tenochtitlán. (As for the lake, almost all of the water has been drained to make room for suburbs.)

Between 1375 and 1521, the Aztecs built a thriving empire with influence that extended throughout the area that is today’s Mexico. The Aztecs were among the world’s first people to require education for all children (even girls!) regardless of social standing. Of course, girls were not taught how to read and write at school (the Aztecs were ahead of their time, sure—but girls reading and writing? That’s crazy talk); their education was focused on home and children. In 1521, the Aztecs were conquered by Spanish conquistador Hernán Cortés, who defeated them partly by giving them smallpox and partly by raising an army of 200,000 indigenous people opposed to Aztec rule.

As for the Incas, their empire started out as a small tribe, but beginning in 1438, they rapidly expanded through the Andes mountain range, eventually controlling most of the western coast of South America. Their empire was notable for its diversity: More than 700 languages were spoken in Incan land, and the empire never really coalesced into a single political entity. In the end, the Incas never got the chance to build a lasting civilization, mainly because in 1532, Francisco Pizarro showed up. With only 200 men and 27 horses, Pizarro should have been crushed. But, like Cortés, he had two things working to his favor: smallpox and thousands of indigenous people resentful of Incan rule.

Both empires’ stories finish sadly—but then neither Pizarro nor Cortés fared all that well, either. Pizarro was assassinated in 1541, and Cortés spent much of his later life suffering from bouts of insane paranoia.