I went to a fairly old Catholic school in the suburbs of Los Angeles that had a large U-shaped building/library/hall/classrooms attached by a common hallway but there were hidden passageways that either led to the outside or allowed you to bypass entire rooms without anyone seeing you. We had a pretty cool school janitor that showed us these passageways after school one day. The one I remember had an entrance from my 4th grade classroom storage closet.

Needless to say, that entire school year I was terrified of that closet. We were told they were used by the nuns to get from the adjacent convent into the classrooms or hall faster. They were creepy AF to be in because they were narrow and even as kids we had to walk single file to go through them. Shortly after I graduated the building was damaged in an earthquake and was demolished. I would love to see the building plans for that original structure because those passageways were built when the building was made.

Thats fascinating. Are they truly that old? Why didn't the older church Fathers not come out with this, or not know about them? They apparently were the ones who initially asked the city to fill them in with cement.