Architecture, such as that seen at Machu Picchu, textiles, pottery, and feather and metal work were among the Incas' greatest artistic achievements. It dates from the time of two of the most well-known Inca groups, Pachacutec Inca Yupanqui (1438–711) and Tupac Inca Yupanqui (1438–711). (1472-93). The best known example of Inca architecture is the city of Machu Picchu in Peru, which was built around 1450 - 1540 AD by the armies of the Inca emperor Pachacuti. This incredible achievement would not have been possible without a sophisticated system of building codes that went beyond what we know today. The Inca used natural rock formations as a basis for their buildings, using many different shapes and sizes of stones to create structures up to 20 stories high. The Inca were some of the first people to use concrete in their buildings. They mixed volcanic ash with lime to make a hardener that could be poured into wooden molds to make walls that were extremely strong but also very heavy. The Inca used this technique to build bridges, stairs, and buildings for military purposes. In addition to being used for construction, Concrete was also widely used by the Inca as a medium for painting pictures on the walls of their temples and palaces. These paintings covered almost all of Machu Picchu except for the areas that had been damaged or destroyed by time or humans.