One of the stairwells that are thought to be so narrow such that an invading soldier would not have been able to fight and defending the caves, theoretically, would have been easier. The Romans were patient armies. They would have just stayed on the surface with a small force and would have starved them out—at which point the narrow passageways would have worked against the inhabitants. Note also the marks in the walls from the constructors hacking the passageways out of the rock. The stairs are also hacked out of rock.