As for these things which ye behold, the days will come, in the which there shall not be left one stone upon another, that shall not be thrown down. One stone upon another - This was literally fulfilled. See Matthew 24:2.
Related Commentaries of Luke 21:6
Luke 21:6
6 As for these things which ye behold, the days will come, in the which there shall not be left one stone upon another, that shall not be thrown down.