What makes the Inca Empire so fascinating to archaeologists and historians is that they specialized in achieving the impossible. They conquered a huge empire without the use of wheeled vehicles or horses to pull them. They had no system of writing but managed somehow to maintain administrative control of far-flung provinces thousands of miles from their capital. Without survey instruments, blueprints, photographs, and machines for construction, they were still able to produce magnificent mountainside terraces, highways, bridges, cities, towns, temples, and royal estates. Many of their projects were built in seemingly impossible places, including sheer cliffs, steep mountain peaks, and raging rivers. And they did this in a remarkably short time of less than 100 years.
Relays of runners could carry news of a revolt swiftly from a distant province to the capital. Inca soldiers stood guard at outposts throughout the empire. Within days of an uprising, they would be on the move to crush the rebels. Ordinary people were restricted from using the roads at all.