Domenico Bettinelli linked this, and I have to admit, it's pretty cool.
It is interesting to me in another context, too. I've been reading Robert Hugh Benson's Come Rack, Come Rope about the Elizabethan persecution of Catholics. One of the minor characters in it is a cabinetmaker who specializes in making secret bolt-holes and passages in houses to hide priests and sacred vessels in.
Not that I think it will come to that. Not in my lifetime, anyway.
I do think we will see a renewed effort to drive Catholics from the public square, though. I am particularly concerned about three areas where the Catholic church does good works: hospitals, orphanages, and schools. On the subject of hospitals, the church faces pressure in some states to provide abortion services, abortifacients, or referrals to abortion providers, none of which are ethically permissible for Catholics. On adoption agencies/orphanages, the church faces pressure to give children over to gay couples, which is a lifestyle of which the church does not approve. On schools, the church faces pressure to "not discriminate" against teachers who neither believe nor practice lifestyles in accordance with Catholic teaching. It would not surprise me to see, in all three areas, the church driven out of the public square, in my lifetime.
I don't think the religion will be formally outlawed for some time -- hopefully, never. But it might be time to consider those bolt holes and secret hiding places, just in case.
Plus, they're just way cool.