Entirely restored, this fortress dedicated to St Francis Xavier (Navarre's patron saint, born here in 1506) was partially dismantled in 1516 by Cardinal Cisneros, Regent before Charles V's reign could begin. Inside, you can see the Hall of Arms, the Great Hall (17C furniture), and the saint's chamber. It adjoins the keep, or Tower of San Miguel (fine view of the surrounding area). The Chapel of Santo Cristo has a 13C walnut Christ figure and a 15C Dance of Death fresco.