The Incas built a tremendous system of roads that stretched 3,700 miles across the entire empire. They also built a system of channels to irrigate their crops to sustain their population. The Incas used a process of terracing to make the steep mountain sides of the Andes into farmable land. This process was a revolutionary farming movement to support their empire.
The Aztec were very advanced also. They built their capital, Tenochtitlan, on an island in Lake Texcoco. They built out the island and increased the size of Tenochtitlan. They made a plumbing system to carry their waist away from their drinking water . They made floating gardens to sustain their population, which was the largest population out of the three. The Aztecs built roads across the lake on three sides to connect their capital to the rest of their empire.
All of these empires of the Americas were very advanced for their time. These people had accomplished things that the Europeans did, even though they were secluded from the Americas until the late fifteenth century. They revolutionized many aspects of their lives to either honor their gods, connect their empire together, or to grow enough crops to sustain their growing population.