Cusco Peru

I took a taxi to Sacsayhuaman located above Cusco Peru. I was amazed at how precised these heavy stones were put together with such precision. These stones survived numerous earthquakes and in my best guess, thousands of years, and what stones that remained were too heavy to move. I flew back to Las Vegas, Nevada where a coworker explain that by using simple copper tools and using many people moved these rocks. He further explained they had nothing else to do. I replied like farming, hunting, wars, and surviving. The largest stones were over 125 tons. How did they accomplish this?