The normal physical boundaries of existence were nothing to Castiel, but, of course, he could not leave the City, and had only made one attempt to do so. Jimmy, the angel's abandoned, human vessel, received this invitation first, but he could not open it, and being of a practical mind and not an inquisitive one, he put it aside and didn't think of it. The being that was Castiel, however, incandescent, ethereal, and incorporeal, found himself down on the street level of the City, and from thence into a triangular room. He was curious why he was there, and spun some of his energy into a light wavelength perceptible to humans, just in case. It looked like a living firecracker, a white sparkler of almost miniscule size, tumbling and eternally burning in the air at about six feet off the ground.
He waited. Angels were very, very good at waiting.