Shobak Castle is located right off the King’s Highway between Tafilah and Petra. It is a relatively small site but worth a short stopover if you have time between Dana or Karak and Petra. You should go up with the car as the climb is pretty steep. 30 – 45 minutes is probably enough for the visit. On the way back you might visit the guy with the smallest hotel in the world, see picture below 😉 Read some more about it here in German.