Saw my first one over this Thanksgiving break. Random house in the D.C. area I was in had one. Just a normal row home in a suburb and the owner out of nowhere told me about it and showed it to me. He bought the house with it but it was really nicely done with air vents, blast door, etc. I wish I had my camera on me but I didn't. I bet now it would be quite expensive to construct something similar.