The Ciudadela is the great pentagonal fortress that anchors the southwest corner of the old city. Built in the late 16th century under Philip II to plans by the military engineer Giacomo Palearo Fratín, it was one of the most formidable defensive works in Europe. Five arrow-shaped bastions project from the main body, surrounded by ditches and outworks, all oriented to cover every angle of approach.
The fortress never saw serious combat and today the ditches are gardens and the parade ground is a public park. The bastions house contemporary art installations and the whole complex is used for open-air concerts and the famous San Fermín fireworks. Walk the perimeter along the star-shaped moat for the clearest sense of the scale.