Castel, a short form of castello = "castle", is an exceedingly common component in Italian place names. There are many comuni bearing the prefix:

• Castel Baronia , in the province of Avellino
• Castel Boglione , in the province of Asti
• Castel Bolognese , in the province of Ravenna
• Castel Campagnano , in the province of Caserta
• Castel Castagna , in the province of Teramo
• Castel Colonna , in the province of Ancona
• Castel Condino , in the province of Trento
• Castel d'Aiano , in the province of Bologna
• Castel d'Ario , in the province of Mantova
• Castel d'Azzano , in the province of Verona
• Castel del Giudice , in the province of Isernia
• Castel del Monte , in the province of L'Aquila
• Castel del Piano , in the province of Grosseto
• Castel del Rio , in the province of Bologna
• Castel di Casio , in the province of Bologna
• Castel di Ieri , in the province of L'Aquila
• Castel di Iudica , in the province of Catania
• Castel di Lama , in the proviance of Ascoli Piceno
• Castel di Lucio , in the province of Messina
• Castel di Sangro, in the province of L'Aquila
• Castel di Sasso , in the province of Caserta
• Castel di Tora , in the province of Rieti
• Castel Focognano , in the province of Arezzo
• Castel Frentano , in the province of Chieti
• Castel Gabbiano, in the province of Cremona
• Castel Gandolfo, in the province of Roma
• Castel Giorgio , in the province of Terni
• Castel Goffredo, in the province of Mantova
• Castel Guelfo di Bologna , in the province of Bologna
• Castel Madama , in the province of Roma
• Castel Maggiore , in the province of Bologna
• Castel Mella, in the province of Brescia
• Castel Morrone , in the province of Caserta
• Castel Ritaldi , in the province of Perugia
• Castel Rocchero , in the province of Asti
• Castel Rozzone , in the province of Bergamo
• Castel San Giorgio , in the province of Salerno
• Castel San Giovanni , in the province of Piacenza
• Castel San Lorenzo , in the province of Salerno
• Castel San Niccolò , in the province of Arezzo
• Castel San Pietro Romano , in the province of Roma
• Castel San Pietro Terme , in the province of Bologna
• Castel San Vincenzo , in the province of Isernia
• Castel Sant'Angelo, in the province of Rieti
• Castel Sant'Elia , in the province of Viterbo
• Castel Viscardo , in the province of Terni
• Castel Vittorio , in the province of Imperia
• Castel Volturno , in the province of Caserta

and there are further hundreds of places with similar names that are not comuni.