Jesus was talking to the disciples about the things that would take place in Israel in Mat 24.
He even talks about those in Judea fleeing to the mountains at that time.He had stated what they are fleeing from and where they are fleeing to.
Mathew 24
15 When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand).
16 Then let them which be in Judaea flee into the mountains:
According to Daniel 11,the abomination that causes desolation is placed in Jerusalem by the armed forces of the north.The people in Judea flee to the mountains at that time.In revelation we find them in the mountains underground.They have went underground when that abomination which causes jerusalems desolation is placed in Jerusalem by the armed forces.
Revelation 6
15 Then the kings of the earth, the princes, the generals, the rich, the mighty, and everyone else, both slave and free,
hid in caves and among the rocks of the mountains. 16 They called to the mountains and the rocks, “Fall on us and hide us[
f] from the face of him who sits on the throne and from the wrath of the Lamb! 17 For the great day of their[
g] wrath has come, and who can withstand it?”