Muhammad I built the citadel to defend the passage of the Tagus through the Santaver cora, a frontier district of the Emirate of Cordoba. The sandstone it sat on was soft enough to require immediate repairs -- the first renovation dates to 853, just one year after construction. But the location was worth the trouble. The citadel became a center of rebellion against Cordoban authority. In 886, the rebel leader Umar ibn Hafsun used Zorita as a launching point to sack Toledo. Abd al-Rahman III deployed forces from the citadel during his 924 campaign to recover the Santaver cora. For generations, whoever held Zorita controlled the upper Tagus, and no one held it for long without a fight.

In the mid-eleventh century, Al-Mamun of Toledo ceded the area to Alfonso VI of Leon and Castile in exchange for military support against his brother Sancho II. The castle passed into Christian hands when Alfonso took the throne in 1072. Knights Templar seized it in 1124 for the Kingdom of Castile, though they struggled to hold it against Almohad counterattacks. In 1174, Alfonso VIII handed the fortress to the newly founded Order of Calatrava, Spain's first indigenous military order. The Calatravans turned Zorita into something more than a castle: they built monastic quarters within its walls, making the citadel both fortress and monastery, a place where monks prayed in the morning and drilled with swords in the afternoon.

After the Order of Calatrava's devastating defeat at the Battle of Alarcos in 1195, the survivors retreated to Zorita. From behind its reinforced walls -- strengthened with new fortifications and a church built inside the enclosure -- the order regrouped and reorganized. The citadel remained the Calatravans' principal seat until the great Christian victory at the Battle of Las Navas de Tolosa in 1212 allowed them to move south to Calatrava la Nueva. Without its strategic importance, Zorita became a pawn in internal power struggles. In the mid-fourteenth century, rival factions of the Order of Calatrava fought over it, and royal troops besieged the castle in 1334, causing severe damage. By 1443, it had changed hands yet again in another Calatrava schism.

By the late fifteenth century, the nearby towns of Almonacid de Zorita and Pastrana had grown larger and more important, and Zorita's decline was irreversible. In 1565, Ruy Gomez de Silva, the 1st Prince of Eboli, purchased the castle and its surrounding lands. He never moved in. The fortress no longer offered conditions fit for residence -- the sandstone that had required repairs since the year it was built had finally won its slow argument with the architects. Declared a Bien de Interes Cultural in 1931, the castle stands today as a ruin on its rocky hill above the Tagus, the horseshoe arch at its gate still marking the threshold between the world outside and over a millennium of turbulent history within.