The Incas are known for their massive empire. At the time, it surpassed any european empire at that time. They did not have a system of writing, however they did have a number system by tying knots is a string. They are also known for their many highways that stretch all across their empire, as well as the "rest stops" placed along the way. They were expert fighters, but since they were kind to their conquered cities, most cities usually surrendered peacefully.