Machu Picchu was built as an estate for the Inca emperor Pachacuti around 1450, but was abandoned a century later when the Spanish arrived. Although known locally, it remained unknown to the outside world until American historian Hiram Bingham brought it to international attention in 1911. It was constructed in the classical Inca style and functioned as an astronomical observatory, religious center, and summer palace for Inca kings. Some believe it was the last refuge of the Incas during the Spanish conquest, but archaeologists think it was already abandoned by then due to disease. Machu Picchu is now a Peruvian historical sanctuary and UNESCO World Heritage Site.