Lawrence writes – “You look into the pit, and it appears to have no bottom. As you look deep into the pit you hear the faint voice of a child asking for help. The child has fallen into the pit and cannot get out. While this is a very old illusion, I have never seen detailed construction information on the subject. As I constructed mine, I took pictures and notes and I will attempt to give this information along with pictures of the effect and its construction. I estimate it took about 20 hours to build this effect and cost less than $100 depending on your glass prices.” [via] – Link.