The archaeological site of Atapuerca, around 15km west of Burgos, has long excited students of early human history. Archaeologists made their greatest discovery here in July 2007 when they uncovered a jawbone and teeth of what is believed to be the oldest-known European: at 1.2 million years old, it's some 500,000 years older than any other remains discovered in Western Europe. Unesco World Heritage–listed and still under excavation, the site is open only to visitors with advance reservations.
Ceramics, cave paintings, carvings and burial sites have been discovered here, as well as remains of occupation in the area by Homo sapiens around 40,000 years ago, human settlements from the Neolithic age and even evidence of cannibalism. There’s a diverse program of courses and study groups for adults, students and children (in Spanish).
For a fantastic overview of Atapuerca's discoveries and significance, visit the Museo de la Evolución Humana in Burgos.