The calculated distance (air line) between Acilia-Castel Fusano-Ostia Antica and Marco Simone is approximately 21 miles respectively 34 kilometers.
By car or train, the actual journey to Marco Simone is certainly longer, as only the direct route (as the crow flies) between Acilia-Castel Fusano-Ostia Antica and Marco Simone has been calculated here.
Air line (approximately)
34 kilometers
18 nautical miles