Aerial view of Sierra de Atapuerca, Spain, finishing at an excavation site. This mountain range in the province of Burgos, Spain, is the only site in Europe to contain hominid fossils providing evidence for the presence and way of life of humanity over a period of nearly one million years. The construction of a railroad at the end of the 19th century exposed many sites around the foothills of Sierra de Atapuerca. These have been studied on and off over the past century, leading to a massive advancement in the understanding of human evolution. It is thought that the site will continue to produce evidence of our past well into the future. In 2000, Sierra de Atapuerca was made a world heritage site by UNESCO.