The Incas lived high in the Andes, a mountain range along the western edge of South America. They lived without horses, iron tools, the wheel, or writing. But in less than 100 years, they built spectacular cities of stone and ruled over millions of people.
By 1491, the Incas controlled an area that stretched more than 2500 miles from north to south, but in some places no more than fifty miles from east to west. It included perhaps ten million people. At its height, the empire of the Incas rivaled the Mongols, the Romans, and Alexander the Great.
The Incas adapted to life in the Andes. The climate of their empire ranged from frigid cold to desert or tropical, often within a few miles due to the steep, rocky slopes of the Andes.
The empire included speakers of over 100 languages, but Inca rulers spoke Quechua (pronounced KEH-chuh-wuh), still the speech of 8 to 10 million people in the mountains of Peru, Bolivia, and Ecuador.
Although the Incas did not know how to use iron, they crafted great cities using only stone tools. Inca engineers constructed walls with huge blocks that fit together without the use of mortar. Despite the volatility of their earthquake-prone empire, many Inca buildings remain standing today.