The calculated distance (air line) between Monheim am Rhein and Neustadt/Süd is approximately 12 miles respectively 19 kilometers.
By car or train, the actual journey to Neustadt/Süd is certainly longer, as only the direct route (as the crow flies) between Monheim am Rhein and Neustadt/Süd has been calculated here.
Air line (approximately)
19 kilometers
10 nautical miles