Chris,
Thank you for the pictures; they certainly helped me decide: add some smoke! My portals look somewhat like a couple of the pictures as they have a ledge at the top and are mostly cement; simulated, that is.
Lee,
Thanks for the information; and yes, it helps!
I have finished the portals and the mountain (hill?) side, and now I am working on tying or bridging the two ends of the mountain together. I'll be able to post a few pictures in a day or two.
THX!
Alex