Today I finally witnessed one of my cats using the cat cave that ptarmic wumpus made. They were both very interested in it when I first pulled it out of the box. I finally caught one of them using it!
Thanks again ptarmic wumpus.
P.S. ptarmic - They love playing with the little strip I cut off to make the hole bigger! Every time I see the strip it's in a different part of the house. You could definitely make some great cat toys!