The calculated distance (air line) between Buchholz in der Nordheide and Marienthal is approximately 19 miles respectively 30 kilometers.
By car or train, the actual journey to Marienthal is certainly longer, as only the direct route (as the crow flies) between Buchholz in der Nordheide and Marienthal has been calculated here.
Air line (approximately)
30 kilometers
16 nautical miles