The nation of Israel.
Shortly after Jesus' death Jerusalem was destroyed and the people of Israel dispersed and for over 1900 years the Jewish people were without their homeland. Yet, they are now back in the land of Israel, just as foretold in the scriptures. No other nation of people in history has ever been dispersed from their native homeland for so long, retained their identity, and then returned to their original land as a nation again.
That is the most important sign, but there are others. It's late, though and I'm tired. Goodnight.