Lying between the confluence of the river
Eresma and the river Clamores, the first documented record of
the fortress dates back to Christian writings in the twelfth century.
It was built on top of a rock, that is testament to its military
status. It also served as a residence for Alfonso VIII and this
was the place where the Catholic Isabel was proclaimed Queen of
Castile. In 1764, Charles II founded the Royal College of Artillery
in this location.
In the thirteenth century the building took on an air of Gothic elegance thanks to the work of the architects of John II and Henry IV both of Spain.
The last architectural phase was done in 1587 by the architect Francisco de Mora, possibly in collaboration with Juan de Herrera, who did the Main Courtyard and the Honour School. The edifice has a number of secret passageways that lead to the river and connect several of the city's palaces together.