The calculated distance (air line) between Castel San Pietro Terme and Castel Maggiore is approximately 17 miles respectively 27 kilometers.
By car or train, the actual journey to Castel Maggiore is certainly longer, as only the direct route (as the crow flies) between Castel San Pietro Terme and Castel Maggiore has been calculated here.
Air line (approximately)
27 kilometers
14 nautical miles