The major achievements of the Incan civilizations are in engineering, medicine, and inventions. The Incas were great engineers. The Incan engineers built a system of roads and bridges. As a form of transportation, they created great network roads. Later, the Incas constructed irrigation systems. The irrigation channels supplied water for the crops. In Document 4 it says, "The engineers showed great cleverness and skill in supplying water for the crops since only scattered sections of the land could grow corn." The irrigation channels increased the fertility in the Inca civilization. The Incan civilization developed important medical practices, including surgery on the human skull. The Incas used the medical procedures to mummify the dead. Another accomplishment of the Inca was inventing new technology. The Incas were great inventors. For recording information, they invented the quipu. Later, they invented a calendar which was a tower they called it time makers or time watchers. In the Incan civilization, time was an important essential. The Incans invented many other inventions such as instruments, aqueducts, art, terrace farming, and much more. The technologies, medical procedures, and inventions had a major impact on the Incan