The Inca civilization in South America had incredible infrastructure. I have hiked on their trails during mountain climbing trips.
I have also been to the National Museum of Anthropology in Mexico City. The Aztec displays were amazing. They had human sacrifice problems, but had incredible artifacts that were left behind. I must have used 10 rolls of film at the museum.
I went on to climb Ixtachupatetl, Popocatepetl and Orazaba, high altitude volcanoes and the 7th, 5th and 3rd highest peaks in North America. Popocatepetl was blowing steam when I was there, but then it started real eruptions and has been closed to climbing for maybe 20 years.
Oh, so this was DURING the time of the Inca Civilization. Why didn't you ask them yourself.