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