Jerez' muscular yet elegant 11th- or 12th-century fortress is one of Andalucía's best-preserved Almohad-era relics. It's notable for its octagonal tower, a classic example of Almohad defensive forts, reached through Islamic-style gardens, past a 12th-century mosque-turned-chapel and the 17th- and18th-century baroque Palacio Villavicencio. Fortress hours vary.
You enter the Alcázar via the Patio de Armas. On the left is the beautiful mezquita (mosque), transformed into a chapel by Alfonso X in 1264, though retaining its fountain and horseshoe arches; it's the only remaining one of 18 mosques that once stood in Jerez. On the right, the Palacio Villavicencio, built over the Almohad palace ruins, displays artwork but is best known for its bird’s-eye views of Jerez; the camera obscura inside its tower provides a picturesque panorama of the city.
Beyond the Patio de Armas, the peaceful gardens recreate the ambience of Islamic times with geometric flower beds and tinkling fountains. The well-preserved, domed Almohad Baños Árabes (Arabic Baths), with their star-shaped shafts of light, are particularly worth a look.