It is amazing how technologically advanced the people of Meso and South America were, especially taking into account the fact that they had not developed the wheel. Maybe they did not have a particular need for the wheel, or maybe they had just not advanced to that point yet. Either way, they had many developments that were impressive in their own right.
Of course one of the most well known feats of the Mayans was their eerily accurate calendar system. What some may not know is that this was able to be created due to the Mayans extensive knowledge about astronomy. They even had an observatory to allow them to study the stars and planets with better accuracy. They knew things about planets and their moons, about stars and constellations; they were even able to predict eclipses due to this extensive knowledge. This knowledge, and the calendars it led to, allowed the Mayans to keep track of time and it also allowed them to predict, with stunning accuracy, future events.
The most impressive feat of the Aztecs was their ability to build. They built an entire, extensive city on an island in a lake. Not only that, but their city had intricate systems of waterways and canals. Their building capabilities allowed them to develop their large and powerful empire in just a short amount of time. It also allowed them to develop their food system, which was integral in being able to feed the people of the city.
The most astonishing achievement of the Inca, to me, was the terrace system they created for agriculture. They were able to farm on cliff faces by creating these terraces. This is amazing to me. They not only served to allow people to physically be able to farm land that was once unusable, but it also served to promote their irrigation system. The terrace system was used to control water flow so pools could be created and used to irrigate the fields. So, the terrace system of the Inca allowed them to live in dry, rocky, cliffs, and still be able to grow their own food.