 The "comune" is formed by the municipal seat of Rosignano Marittimo and the "frazioni" – towns and villages – of Castelnuovo della Misericordia, Castiglioncello, Gabbro, Nibbiaia, Rosignano Solvay and Vada.The resort town of La Mazzanta is also included in the municipality.Rosignano Marittimo is twinned with