It was the western hemisphere 's largest empire ever.

With a population of nearly 10 million subjects.

Over an area of more than 900, 000 square kilometers,

its people built massive administrative centers, temples, and extensive road and canal systems.

They did so, in an inhospitable, extreme terrain, all without the use of wheels, horses, iron, or even written language.

Yet, within 100 years of its rise in the 15th century, the Inca empire would be no more.

According to legend, the ancestors of the Inca rulers were created by the Sun God Inti,

and they emerged from a cave called Tambo Toco, leading 4 brothers and 4 sisters

was Ayar Manco, who carried a golden staff with instructions to find a place

where it would sink into the ground showing fertile soil.

After many adventures and extensive searching,

Ayar Manco and his siblings reached the Cuzco valley where the staff pierced the ground.

After fighting off the fierce, local native population, they founded their capital

and Ayar Manco became Manco Capac, the first Sapa Inca, or king of the Incas.

Archaeological evidence suggests that the Incas first settled in this valley around 1200 CE.

They remained a small kingdom until 1438 when they were nearly overrun by the neighboring Chanka tribe.

The Inca king of this time, Viracocha, and his designated heir fled in fear.

But one of his other sons remained, and successfully rallied the city 's defenses.

For his military skill, he became the 9th Inca ruler, assuming the name of Pachacuti, or Cataclysm.

Pachacuti expanded Inca rule throughout the Andes mountains,

transforming the kingdom into an empire through extensive reforms.

The empire 's territory was reorganized as Tahuantinsuyu, or 4 quarters,

with 4 divisions ruled by governors reporting to the king.

Although the Inca had no writing, they used a complex system of knotted strings called Quipu,

to record numbers and perhaps other information.

A decimal - based bureaucracy enabled systematic and efficient taxation of the empire 's subjects.

In return, the empire provided security, infrastructure, and sustenance,

with great storehouses containing necessities to be used when needed.

Great terraces and irrigation works were built, and various crops were grown in at different altitudes,

to be transported all over the empire.

And it was during Pachacuti 's reign, that the famous estate of Machu Picchu was constructed.