Battle of Piedra Pisada On 25 December 1084 , at the Battle of Piedra Pisada , the Taifa of Zaragoza fought and probably defeated the Kingdom of Aragon on the road south from Naval to El Grado . The battle was a minor engagement of the ongoing " Reconquista " of Aragon , the process by which the riverine valleys of the southern slopes of the Pyrenees were gradually conquered and returned , after centuries of Muslim rule , to the control of Christian princes . The ruler of Aragon , who personally led his men in battle at Piedra Pisada , Sancho Ramírez , also ruled Kingdom of Navarre and was a major figure in the contemporary " Reconquista " . The battle is only recorded in two later sources , the Aragonese and Latin versions of the " Chronicle of San Juan de la Peña " . The former says that " in the year of our Lord 1083 . . . [ Sancho Ramírez ] did battle in " Piedra - pissada " with the Moors on Christmas day . " The Latin translation reads : " And [ Sancho ] made battle before " Petram Pisadam " with the Moors , the day of the Nativity in the year of our Lord 1084 . " The two texts differ in the year , and neither specifies the winner of the engagement . The location of " Petra Pisata " was long thought to be Piedratajada , but this is unlikely on linguistic grounds . In a document nearly contemporary with the battle , Peter I of Aragon and Navarre , Sancho ' s son and successor , enumerated the parishes whose tithes belonged to the church of Santa María of Alquézar in geographic order from east to west , placing " Petra Pisata " between Naval and Salinas de Hoz . A forged document from the late twelfth or more likely the thirteenth century purportedly from October 1099 lists the same parishes owing tithes to Alquézar , but in a less orderly manner , naming among them " Petra Piza " . In the thirteenth century , the name of the site had degenerated further to simply " Pisa " , which has been identified with the " coto redondo de Pisa " , a collection of farms south of Naval . The " Reconquista " of the what are today the " comarcas " of Bajo Cinca , Cinca Medio , Ribagorza , Sobrarbe and Somontano de Barbastro was effected along two ancient routes , probably of Roman origin . One followed the river Ésera through the important town of Graus south to Monzón and the lower reaches of the river Cinca . East of the Cinca lay the other route , connecting Boltaña and Barbastro . The " Reconquista " of the Cinca valley and surrounding territory to its west was rapid . By 1049 Perarrúa was the most advanced position on the Ésera , held by a don Suniero , and by 1062 Laguarres was the most advanced position on the Isábena . Both faced the formidable city of Graus , which was unsuccessfully besieged as early as 1055 and again in 1063 with disastrous results , finally falling to the Christians on 14 April 1083 . By 1083 all lands north of the Sierra de Estada were in Aragonese hands . On the other side of the Cinca the town of Castejón de Sobrarbe fell in 1057 and that of Abizanda in 1059 , but further progress was slower . Naval , which was essential to the defence of Barbastro ( which was briefly occupied in 1063 – 64 ) , and Arguedas were not taken until 1084 , and shortly lost to the Moors for a decade . Since Piedra Pisada ( Pisa ) lies on the road south from Naval , the Aragonese army would have had to bypass an important enemy fortification in order to fight there , unless Naval had already been taken . It is most likely therefore that the date of 1084 found in the Latin chronicle is correct . Since the loss of Naval posed a threat to Barbastro , it is likely that forces from the " taifa " were sent to retake it later in 1084 and that it was these forces which Sancho Ramírez met on the road south from Naval . Since neither surviving record of the battle , both Christian , records the outcome and Naval is known to have lapsed out of Christian control soon after its conquest , it is probable that the battle was a loss for Sancho . In the aftermath of the defeat at Piedra Pisada , in 1085 Sancho invested his son Peter as king of Ribagorza and Sobrarbe under Aragonese suzerainty . Estada was conquered in July 1087 , and Monzón with the aid of some defecting Muslims in 1089 . In 1095 Peter accepted the surrender of the garrison of the castle Naval , and in October 1099 he made an accord with its Christian populators .