The site of the Alcázar of Segovia, on the top of a rock shaped by the rivers Eresma and Clamores, shows the military origins of this fortress which, for centuries, was impregnable.
The oldest testimony we have of the Alcázar is a document dating from the early days of the 12th century (1122), a short time after the town had been recaptured by Alfonso VI, which refers to the fortress as a hill-fort on the Eresma. A short time later, in a letter of 1155, it was already being referred to as "Alcázar". However, it is more than probable that the fortress had existed in earlier times, possibly since the Roman occupation, because granite blocks similar to those of the Aqueduct have been found in the course of recent excavations. In residencies of the monarchs of Castile, partly due to the beauty of its location and its unquestionable military secureness, and partly for its proximity to the famous hunting-grounds in the mountain forests.
Alfonso X "The Wise" showed a special liking for Segovia and made the Alcázar into one of his favourite residences until the later days of his life, when the Parliament was held in this town which had remained loyal to him.
In the 14th century, Segovia bore witness to the struggle between different noble factions which the Alcázar did not escape; the new usage of artillery forced it to reinforce its walls and extend its defences.