And Jesus being come out of the temple, went away. And his disciples came to shew him the buildings of the temple. And he answering, said to them: "Do you see all these things? Amen I say to you, there shall not be left here a stone upon a stone that shall not be destroyed."
THE END OF THE WORLD: The exact fulfillment of our Lord's words about the destruction of Jerusalem is a pledge that what He foretold about the end of the world and His second coming will be equally fulfilled. The signs which precede the end of the world will be similar to those which preceded the destruction of Jerusalem: wars, sedition, and earthquakes. The Gospel will first be preached to all nations (although our Lord does not say that all will accept it); but there will be a great apostasy before the end of the world: false Christs and false prophets shall appear, and many shall be seduced. The laws of the universe will be upset, and then shall be seen the Cross in the heavens, and the Divine Judge will come in power and glory. All the dead will be called from their graves to appear before Him, and heaven and earth shall pass away -- or be changed. "The fashion of this world passeth away," says St. Paul (1 Cor. 7:31); while Peter writes thus: "For we look for a new heavens and a new earth according to His promises" (2 Peter 3:13). God will not destroy either heaven or earth, but He will transform and renew them.
[From 'A Practical Commentary on Holy Scripture' by Bishop Knecht, D.D.]
(1899 Douay-Rheims Bible)