The Temple
King Herod had spent decades rebuilding the Temple in Jerusalem. It was huge, covered in white stone and gold, and some of its blocks were the size of a bus. Nobody could imagine it gone.
What Jesus said
"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 thrown down."
Matthew 24:1 to 2 · around AD 30
How it would happen
He gave details. Coming into Jerusalem, he wept over the city:
"For the days shall come upon thee; and thy enemies shall cast a trench about thee, and compass thee round, and straiten thee on every side, and beat thee flat to the ground, and thy children who are in thee: and they shall not leave in thee a stone upon a stone."
Luke 19:43 to 44
And he told his followers what to do when the moment came:
"And when you shall see Jerusalem compassed about with an army: then know that the desolation thereof is at hand. Then let them that are in Judea, flee to the mountains: and let them that are in the midst thereof, depart out."
Luke 21:20 to 21
AD 70
In AD 66, the Jews revolted against Rome. Roman legions marched on Jerusalem, and in AD 70 the general Titus laid siege to the city.
The Jewish historian Josephus was there. He records that Titus built a wall right around Jerusalem so no one could get in or out (Jewish War 5.12), and the city starved. When it fell, the Temple burned. Titus then ordered the city and the Temple demolished (Jewish War 7.1).
The ones who listened
The early Church historian Eusebius records that the Christians in Jerusalem were warned to leave before the war, and fled across the Jordan to a town called Pella (Church History 3.5). When the army surrounded the city, they did exactly what Jesus told them to do.
Why this is a big deal
When Jesus said it, the Temple was standing, in perfect condition, at the centre of the Jewish world. Within forty years, within the lifetime of the people who heard him, it was gone, just the way he said.