The calculated distance (air line) between Ondarroa and Aretxabaleta is approximately 20 miles respectively 32 kilometers.
By car or train, the actual journey to Aretxabaleta is certainly longer, as only the direct route (as the crow flies) between Ondarroa and Aretxabaleta has been calculated here.
Air line (approximately)
32 kilometers
17 nautical miles