August 2002: We had a cement footer poured, then built short cinderblock walls. The interior of the greenhouse is 7½ feet wide by 21 feet long.
The wire frame is made from five 16 foot x 52 inch cattle panels (which have countless uses and are available at farm stores) that are fastened together with tie wire. The ceiling is about 8 feet high in the center.
The finished greenhouse in April 2003
The greenhouse interior in April 2003
The greenhouse interior in May 2003
There's more information about constructing the greenhouse in the comments section of this post.