
One centimeter on my model is equal to one meter in Castel Del Monte. This means I measured the balsa wood to be 3.11 cm by 19.65 cm for each face of a tower because the actual wall is about 3.11 meters wide by 19.65 meters tall.
We made eight towers and eight walls to form an octagonal castle to look like Castel Del Monte. These were glued to the base foam board right on the blueprint.
For measuring, marking and cutting the lengths of each piece of wood or foam board I used a ruler and a right triangle and a special Exacto tool like a surgical knife. My fingers got sore from the cutting work.

http://ftp.iwr.uni-heidelberg.de/~Susanne.Kroemker/ART_PROJECT/HTMLpages/castel.html#aquarell