The Incas were an amazing people, as were also their pre-Inca predecessors in the ancient land of Peru, one of the cradles of civilization on Earth. Apart from the Mita, which you correctly point out, another keystone in their system was the good old potato or "papa", as it is known originally. If the Aztecs or Mayans built their societies on maize ("maíz"), the Inca empire was built on "papa", allowing this food system to be able to cope with extreme weathers and long distances all over the Tawantinsuyo, making it ideal for storing and stocking up. The development of agriculture and civilization are closely linked-up and the "papa" was a cornerstone in this process in ancient Peru, where the tuber crop was domesticated into thousands of different varieties. Truly, a gift from the Incas to the world...