Evidence of prehistoric human habitation has been unearthed in hillsides in some areas of "Narros del Castillo" (Ávila), and in "Siete Iglesias de Trabancos" (Valladolid), dating from the Quaternary period, and have been further pinpointed as originating in the Lower Paleolithic era. At both sites, collections of lithic stone artifacts knapped during the Acheulean period are found on the surface (not as a result of archeological excavation), including centripetally knapped lithic cores, others displaying non-arranged lithic reduction, as well as lithic flakes characteristic of both the Levallois and Kombewa techniques, chopping tools, and handaxes.