The stunning ruins of Machu Picchu, situated in the Andes Mountains between two sharp peaks almost eight thousand feet above sea level, continue to attract visitors from around the world (Figure 8.1). Once a palace and royal retreat for the conquering Inca ruler Pachacuti Yupanqui, the complex was begun in the mid-fifteenth century CE and remained occupied until shortly after the Spanish arrived in the following century. Under Pachacuti Yupanqui, from their Andean home city of Cuzco, the Inca extended their control and built a large empire in Peru. Later rulers continued this expansion, bringing much of western South America under their rule. While the Inca Empire was impressive and politically, religiously, and technologically sophisticated, it was merely the last of many Andean civilizations and cultures stretching back thousands of years. Indeed, these South American civilizations were part of an even larger number of cultures, empires, and architectural traditions that spanned the entire Western Hemisphere and were built by the descendants of migrants who reached the Americas several thousand years ago.