On the floor of the tunnel was a wobbly bridge. The drawing on the left shows how we did that and pretty much speaks for itself. Click on it for a larger image. Basically you just have to make sure that the center plank is a couple of centimeters higher than the side planks. But be careful with how high you make it because you wouldn't want anyone to fall. A motion detector picked up when guests approached the box that the skeleton was hanging in and triggered a light above him to go on. At the same time, a switch was activated by stepping on a spot on the bridge right in front of the skeleton. This triggered a recorder that played a message greeting the guests.
The picture on the left shows the canvas that a friend of ours, Peter, painted for the entrance to the tunnel. He used two old curtains that he dyed gray and painted a stone castle wall and entrance on it. The night of the party, we placed two lighted pumpkins on either side of the entrance. Hopefully we'll get better pictures of them next year. On the right side, you see a picture of the finished tunnel from the inside. In the picture you can see the two sheers that we used for the scrim boxes but that's only because of the flash. In the dark, you couldn't see them and they blended in with the black walls.