While staying in Cusco we took several bus tours to nearby places in what is called the Sacred Valley of the Incas. There we saw some Inca structures and terracing which they used to do farming on hillsides and got some some good views of the surrounding countryside. The Incas were good architects and engineers (and astronomers). Their mortarless stone structures lasted well and some were used by the Spaniards as foundations for their buildings.
The first day was tough since we had just gotten to the higher altitude of Cusco (11,300ft) and some of these sites were even higher. Most people had trouble sleeping the first night. I could hear and feel my heart beating for hours while lying awake in bed. Another day in Cusco with nothing much happening on the first one would have been better.