The calculated distance (air line) between Koropí and Néa Smýrni is approximately 9 miles respectively 15 kilometers.
By car or train, the actual journey to Néa Smýrni is certainly longer, as only the direct route (as the crow flies) between Koropí and Néa Smýrni has been calculated here.
Air line (approximately)
15 kilometers
8 nautical miles