What were some contributions of Inca civilization?

The main contribution of the Inca was their architecture and engineering, and they constructed some of the most marvelous and renowned structures by any civilization; But they also contributed to many other things such as building many extensive road ways, bridges, and aqueducts that they constructed all by themselves. The Inca were also very unique in their ways of governing overtaken tribes, and they made extensive farming areas using terraces. They had even fit large stones together to build their cities; There was no mortar needed and the structure could withstand earthquakes.

The Inca empire was the largest empire in Pre-Columbian America. The Andean civilization, which was estimated to have formed from as early as 4th century BC, is regarded as the first civilization in South America. It is 1 of 5 civilizations in the world considered by scholars to be “pristine”, that is indigenous and not derivative from any other civilizations. In the middle of the 15th century, the Inca ruler Pachacuti began a series of conquests which were then continued by his successors, to unite most of the Andean cultures into the Inca Empire. At its greatest, the Inca Empire incorporated large parts of modern day Peru, Chile, Ecuador and Bolivia. As well as north-west Argentina and south-west Columbia.

The Inca invented the rope suspension bridge independently from outside influences. The Inca used various means to bridge water courses of which the most famous is their rope bridges. The Inca invented the rope suspension bridge independently from outside influence. However, suspension bridges had been in use for long in mountainous regions in Asia.

The Inca are considered to be the first people who developed the technique of freeze-drying to preserve food for long periods of time. They used the freezing temperatures at night in the Andes to freeze frost-resistant varieties of potatoes and then exposed them to the intense sunlight of the day. They called these potatoes Chuno, which was extremely durable and could be kept in the storehouses for up to 4 years.

The Inca successfully managed their vast empire without using money or having an internal market economy. The Inca did not use money as an exchange unit or markets to trade, though they did trade with outside regions. The local farmers in the empire worked on the land but they were allowed to keep only one portion of the produce with the remaining two portions being used to support the Inca government and religious leaders. All adult men in the empire were required to perform mandatory public service known as Mita.  In return the Inca government provided security, food, housing, clothing, education, occasional feasts and technical help to increase agricultural productivity.

can you show the map , i'll be able to update my answer

b) to encourage free trade