Around the year 900, the Arabs built the castle of Pietrarossa, a fortress in a strategic position in the heart of Sicily, on a limestone ridge overlooking the Salso Valley - a communication route open to the south - and visually connected to the castle of Pietraperzia, in an area rich in wheat production.
The area surrounding the castle still bears the name Murra, a transliteration of the Arabic mnra meaning “red” - the same etymological root as the Alhambra of Granada (al-mnra, the red one) - a word that referred not only to a color but also to a quality: the supremacy of the fortress over the others in the region.
Indeed, throughout the Middle Ages, the castle was the scene of significant events - episodes of the Sicilian Vespers War, meetings of rival barons, and the partition of Sicily among the Four Vicars - all emphasizing its strategic role in central-southern Sicily. Partly collapsed in the 16th century, the castle was later used as a stone quarry to build the Franciscan convent, cemetery chapels, and houses in the Angeli district. For this reason, its shape and dimensions can now be reconstructed only in part.
Remains of masonry along the rocky ridge suggest that defensive walls enclosed a wide area within which three towers stood - symbols of the city - of which only parts of the central and northern watchtowers remain. Excavations have uncovered rainwater cisterns, one of which was used as a prison until at least the late 15th century.
Nineteenth-century excavations revealed the entrance to an underground passage, probably a secret escape route from the castle, which was soon sealed off again - feeding numerous legends about a buried Caltanissetta, with secret tunnels crisscrossing the city in a hidden network.
Among the castle’s ruins, shortly after its collapse, a tomb was found containing the body of Princess Adelasia, niece of King Roger, wearing a green velvet dress and a metal crown. The discovery, recorded in contemporary chronicles, gave rise to the legend of the beautiful Norman princess, who died unhappily in the castle of Pietrarossa and whose ghost is said to still wander among the ruins of the tall towers.