The calculated distance (air line) between Castel San Pietro Terme and Castel Bolognese is approximately 12 miles respectively 19 kilometers.
By car or train, the actual journey to Castel Bolognese is certainly longer, as only the direct route (as the crow flies) between Castel San Pietro Terme and Castel Bolognese has been calculated here.
Air line (approximately)
19 kilometers
10 nautical miles