The remotest roots of Caltanissetta are as yet uncertain. Relics from the Bronze Age and several cave-sepulchres seem to attest to prehistoric settlements. Some historians held that the city origins might be somehow related to the ancient Nissa, situated on a mount called Gibil (or Gabel). The earliest documented information goes back to the Norman conquest, dated 1086, when Count Roger took the Castle of Pietrarossa. A remarkable urban development was recorded in the 15th century, Caltanissetta extending its territory beyond the city walls.