This is an old house, with an attached shed. There has always been a passage way under the porch and into the shed. We call it the tunnel, and have sort of constructed a more permanent version so the cats can shelter there and come in themselves through a cat door in the shed/kitchen door.
I've started feeding Charlie at the inside end of the tunnel, to the great annoyance of the other two cats. *g* And this morning, since it was 20 deg out, I made a cat bed for him