Battle of Atapuerca The Battle of Atapuerca was fought in 1 September 1054 at the site of Piedrahita ( " standing stone " ) in the valley of Atapuerca between two brothers , King García Sánchez III of Navarre and King Ferdinand I of Castile . The Castilians won and King García and his favourite Fortún Sánchez were killed in battle . Ferdinand reannexed Navarrese territory he conceded to García 17 years early after his brother ' s assistance at Pisuerga . Precedents . After the death of Sancho III of Navarre , his empire was divided with Ferdinand receiving the then County of Castile and García , the Kingdom of Navarre . In 1037 , Bermudo III of León died without descendants in the battle of Tamarón against his brother - in - law Ferdinand of Castile . Ferdinand inherited the title of King of León , entering the city of León on 1038 . He rewarded the help of his brother García with Castilian territories from Oca to the gates of Burgos , from Briviesca to the valley of Urbel , from Castrobarto to Bricia and from the Nervión river to Santander . Versions . " Chronicon Silense " . The monk of Silos wrote several decades later that an envious García attacked Ferdinand who was visiting him at Nájera during his illness . Recovered , García visited back Ferdinand to make peace . Ferdinand set him in chains and locked him in a tower in Cea . The Navarrese escaped and declared war , rejecting the Castilian embassies . García was buried in the nearby village of Agés and his tomb was recently discovered in the church there . The hosts of Castile and León were in Atapuerca , three leagues eastwards from Burgos , already in Navarre . García had with him Moorish auxiliary troops and maybe his brother king Ramiro I of Aragon . " Annals of Compostela " . The " Annales compostellani " attribute the death of García to one knight of his , Sancho Fortún , " whom he [ the king ] , had offended with his wife " . Several in the Navarrese retinue preferred death in combat , and also the murderer , lord of Funes , Navarre , died in battle . " Crónica Najerense " . The " Crónica Najerense " mentions relatives of Vermudo , who furiously engaged García , disobeying Ferdinand ' s instructions to take him alive . The Navarrese kept however their places until night and took the corpse to bury him in Nájera . The proclaimed on the spot the new king , an adolescent Sancho de Peñalén . Other version . Ferdinand is in this version the reckless brother and covets the " Asturias of Santander " , Old Castile , Briviesca and Rioja . Ferdinand visited his ill brother , but suspecting him fled . García visited an ill Ferdinand then , wishing to dispel his suspicions , but was locked in Cea . Upon escaping , he took his troops and some Moors into Castile . In Atapuerca the peace talks failed . Two traitor soldiers ( one of them , Sancho Fortún ) , wounded him lethally . Ferdinand conceded the transport of the corpse to Nájera , took Briviesca , Montes de Oca and part of Rioja . The border of Navarre was set by the Ebro , and the new king Sancho IV of Navarre became Ferdinand ' s vassal . El Cid ? Some sources mention El Cid as one of the battlers , but being born on 1043 or 1048 he would be too young . Later history . In 1940 a commemorative inscription was carved on a 6 , 000 - year - old menhir at the site . Since 1996 , the people of Atapuerca and neighbour towns reenact the battle on the last or previous Sunday of August .