Over the last thirty years research on Sicilian Greek towns has substantially progressed. Today we are aware of the main topographical features of the colonial settlements, Achean or classical. Research has yielded weIl detailed results, especially on town planning and the organisation of urban space. It has benefitted from a major contribution, aerial photography, and particularly on such ancient sites as Syracuse, Casmene, Camarina, Agrigento and Selinunte : town planning on a regular plan has been evidenced, typical of so called « colonial » settlements or « hippodomian ». In this way aerial photography has allowed the study of these urban settlements, basic advances of our western civilisation, to begin in earnest.