As you arrive on the N620, you will see the imposing outline of the castle of Simancas, both medieval by its crenellated wall and Renaissance by the elegance of its tower and roof. Built in the 15C on a former alcázar by Admiral Alonso Enríquez, the castle was used by the Catholic kings to house a state prison, before finding its final vocation, that of the kingdom's archives, which today contain some 35 million documents!