Steel Heritage Stereogram.
Stereograms contain hidden 3-D images. To see the image, relax your eyes to look at a point about a foot behind the screen and wait until the image forms.

 Hint:

Foreground image from SIHC. Depth information in Photoshop. Background image from another image on this site. Stereogram constructed with Hidden3D. Copyright © 1998, Mary Shaw
medium red bar
light red bar

Experimental images on the prototype section of the Allegheny Trail Alliance site.
Copyright © 1998 by Mary Shaw. Permission granted for personal use. All other rights reserved.