The biggest problem is the lack of clear detail photos of the pylons. Finally I discovered more by chance than anything else in the Rieter archive an original plan with all the mesurements. With this new informations I could finally draw some plans in 1/50 (approx. O-Scale). First I'was playing with the idea of doing it in 1/32 but in that case it would have covered the whole writing desk. 
Each stone has to be carved first by hand bevore the casting. I used a wire brush to to reproduce the chiseling pattern of the sandstone.