International Day for Monuments and Sites © Dora Dalton/Getty Images
Located high in the Andes Mountains, Peru"s Machu Picchu is believed to have been an estate for the Inca emperor Pachacuti, who ruled in the mid-15th century. This "Lost City of the Incas" is one of the world"s most famous archaeological sites, an engineering marvel, built without mortar, metal tools, or the wheel. As an icon of Inca civilization, it is a perfect fit for UNESCO"s International Day for Monuments and Sites, which has been celebrating important cultural heritage sites for 40 years. Landmarks such as the Pueblo Indian dwellings of Mesa Verde, the Taj Mahal, the Great Pyramid of Giza, and the Parthenon give us the opportunity to look back at the cultures that came before us and preserve their memory for future generations.