The Middle Ages
In the early Middle Ages the valley formed part of Castella Vetula, or the original Castilla, the Al-Qilá of the Muslim chroniclers, and, during this period, it would be the object of intense agrarian colonisation by peasantry and small monastic communities such as San Emeterio and Celedonio of Taranco. At the same time as this agricultural expansion, made possible by a system of building small dams in the rivers, the inhabitants had to face Muslim invasions and raids aimed at halting the economic and demographic development already underway. The origins of several local villages can be traced back to this time, for example Taranco, Ordejón and Burceña, which are mentioned in the founding Act of the Taranco monastery, dated 15th September 800 AD.
Throughout the twelfth and thirteenth centuries, the height of the Middle Ages, the hamlets underwent a process of feudalism at the hand of ecclesiastical institutions – The Order of St John of Jerusalem and the monasteries of Oña, Tabliega and St Millán de la Cogolla – and local lines of nobility – Vivanco, Ortiz, Angulo, Gil or Vallejo, which took control of lands and village jurisdiction. This time also corresponds with the introduction of the Romanic style, seemingly linked with the opening of a secondary route of the Camino de Santiago, and with the establishment of Villasana in what is today the old quarter of the town as well as that of other villages throughout the Valley.
In the late Medieval era, the fourteenth and fifteenth centuries AD, the construction of various towers took place in different villages of the valley, and there were outbreaks of bloody partisan fighting, lead by the principal noble families which were by then established in the area, the Velasco and Salazar families, each backed by small local family groups connected to them through vassalage.