Bar Kokhba hiding complexes
The Bar Kokhba hiding complexes are underground hideout systems built by Jewish rebels and their communities in Judaea and used during the Bar Kokhba revolt (132–136 CE) against the Roman Empire. The hiding complexes are believed to have played a significant role during the revolt, particularly in Judea proper.
Source: Wikipedia — Bar Kokhba hiding complexes (CC BY-SA 4.0)