The Atapuerca Mountains (Spanish: Sierra de Atapuerca) is a karstic hill formation near the village of Atapuerca in the province of Burgos (autonomous community of Castile and Leon), northern Spain. In a still ongoing excavation campaign, rich fossil deposits and stone tool assemblages have been discovered which are attributed to the earliest known hominin residents in Western Europe. This "exceptional reserve of data" has been deposited during extensive Lower Paleolithic presence, as the Atapuerca Mountains served as the preferred occupation site of Homo erectus, Homo antecessor, Homo heidelbergensis and Homo neanderthalensis communities. The earliest specimen so far unearthed and reliably dated confirm an age between 1.2 million and 630,000 years.