What is the largest? I don't think you should regard the gnomon as being the criterium, it can be much longer than necessary. I would suggest: the largest actually used sundial face. The larger this face the larger the gnomon will be (in general).
The largest I ever saw was in Munich, Germany. It is the inner court of the Deutsches Patentamt, measuring 30x60 meters. The gnomon is a innercorner of the roof located at the 4th (5th?) floor. Thibaud Taudin-Chabot <[EMAIL PROTECTED]>
