In the neighbourhood are the great quarries in which the slaves not
only worked, but also lived. They were made to cut the walls so that
they inclined inwards, and therefore could not be climbed.
The only entrance to the quarries was by ladder, so there was no
escape for a man once he got in there.
There are huge caves cut in the walls of the quarries in which the
slaves lived, and one of these caves has been cut into a narrow cleft
exactly on the principle of the inside of your ear. So that anyone
sitting at the top of the cleft can hear every word that is being
spoken or even whispered in the cave below.
It is said that Dionysius, the ruler of Syracuse, had this made so
that he could sit in the cleft (where there is a little chamber with
private door) unknown to the people in the cave, and there he could
overhear all that the prisoners talked about and plotted among
themselves.