The Incas built the estate around 1450, but abandoned it a century later at the time of the Spanish Conquest. Although known locally, it was not known to the Spanish during the colonial period and remained unknown to the outside world before being brought to international attention in 1911 by the American historian Hiram Bingham. Since then, Machu Picchu has become the largest tourist attraction in South America. Most of the outlying buildings have been reconstructed in order to give tourists a better idea of what the structures originally looked like. By 1976, thirty percent of Machu Picchu had been restored. The restoration work continues to this day.