In this paper, we suggest a generic city description model suited for purposes like semi-automatic city modelling and urban layout evaluation. The generic city model refers to basic vital functions of a (computable) city.  Feature patterns are used to extend the generic city model with global and local characteristics. The Hellenistic cities serve as a platform for a first implementation to test a semi-automatic city model generation. As a result four cities are reconstructed as a first example of our ongoing work, Miletus, Knidos, Priene and Olynthus. Future work will deal with the application of the generic city model to the performance simulation of contemporary urban layouts.