Summary The politeia established in Athens in 317 after a covenant between Cassander and Demetrius of Phalerum was variously described by ancient authors as a tyranny, an oligarchy, and a democracy. Even among modern scholars there is no agreement about its definition. A close study of the architecture of the so-called regime of Demetrius and a comparison with the almost contemporary constitution of Cyrene, imposed on the African town by Ptolemaeus I, lead us to characterize it as a mixed constitution, (...) which balanced elements from the three principal types of political organisation. This experiment had a strong impact on the Hellenistic and Roman political traditions, as testified by Cicero, who recalled Demetrius as the last great Athenian lawgiver and inventor of the blended constitution. (shrink)