Mark 13:29

So ye in like manner, when ye shall see these things come to pass, know that it is nigh, even at the doors.

The verse belongs to a discourse in which the destruction of Jerusalem is blended with the events of Christ's coming and the end of the world. The signs and events in that discourse point first to Jerusalem's destruction and also beyond it to the final judgment. It is given both for the disciples who first heard it and for people living in the last scenes of earth's history.

As the fig tree's branch yet tender and putting forth leaves shows summer is near, so when the foretold things come to pass believers will know Christ's coming is nigh, even at the doors. When the predicted signs occur, the event they announce is near. These things are deception by false Christs, wars and rumors of wars, nation rising against nation, earthquakes, famines, troubles, persecution and hatred, the gospel published among all nations, the abomination of desolation, great affliction, false signs and wonders, the darkening of sun and moon, falling stars, shaking of the heavenly powers, and the Son of man coming in clouds with angels to gather the elect.

The warning applies to the destruction of cities filled with sin, where earthquakes, fire, and floods will display God's authority. Human wealth, buildings, and devices will not protect people from His judgments.