The calculated distance (air line) between Castel San Pietro Terme and Portomaggiore is approximately 23 miles respectively 38 kilometers.
By car or train, the actual journey to Portomaggiore is certainly longer, as only the direct route (as the crow flies) between Castel San Pietro Terme and Portomaggiore has been calculated here.
Air line (approximately)
38 kilometers
20 nautical miles