Monday 15th July is the 9th of Ab in the Jewish calendar, the date on which the Jews mourn the loss of the Temple in the First Jewish revolt. Josephus records how during the revolt many Jews took refuge in underground hiding places:
So now the last hope… was in the caves and caverns under ground; whither, if they could once fly, they did not expect to be searched for; but endeavored, that after the whole city should be destroyed, and the Romans gone away, they might come out again, and escape from them. This was no better than a dream of theirs; for they were not able to lie hid either from God or from the Romans. War 6.370
Now archaeologists have discovered what might be one such passage:
a disused cistern which contains fragments of pottery
Emphasis on the might.