Very small amounts of archaeological finds suggest that settlement on the site was at least as early as the 14th Century CE, although the later settlement built on top of these early layers has destroyed all but a few tiny traces.

Foundation of a Hellenic military colony on the defensive hill by Alexander the Great’s Macedonian Greeks either during Alexander’s campaign through Palestine in 332BCE or as they returned west after Alexander’s death in Babylon in 323BCE. 

The name “Gadara” is not Macedonian Greek, but adapted from a Semitic word meaning “fortification” suggesting that the military colony took over a pre-existing stronghold / settlement securing this area of the land route between southern Syria and the ports on the north Palestine coast.

Earliest known line of city walls was built surrounding the main settlement hill. Although remains of a Hellenic distyle temple probably dedicated to Poseidon outside these walls show that some parts of the city remained unprotected.

Greek historian Polybius described the city as a military fortress the “strongest of all places in the region”. Polybius’ description tells us that Gadara was already an important place with cultural and administrative influence over the surrounding area.

A long siege in 218 BCE by Seleucid King Antiochus III leads to Gadara's capture. But shortly after Ptolemy IV defeated Antiochus III at the  Battle of Raphia forcing Antiochus III to withdraw north of Lebanon returning the Gadara to the Ptolemaic Kingdom

Construction of the first aqueduct bringing water to the city from the Ain Turab spring c13km east of Gadara. Prior to this the water supply for the city relied on rain water stored in water cisterns cut into the rock of the settlement hill. 75 cisterns have been found to date, some as large as 450 cubic meters. Many of the ancient Hellenic water cisterns were still being used to store rain water until the relocation of the village in the 1980s!

An area north of the settlement hill was artificially flattened and a podium temple built in the centre surrounded by a Tenemos (large temple sanctuary courtyard). The city walls were extended to surround this new area including the addition of the eastern (Abila) gate. The temple was likely dedicated to the god Zeus Olympios as within the temple sanctuary archaeologists found a marble statue of enthroned Zeus Olympios / Nikephoros carved in the same style as the gold and Ivory statue of Zeus at Olympia. Images of Zeus also feature prominently on Hellenic period coins minted at Gadara. The location of the temple complex would have made it very prominent on the skyline of the city for a considerable distance.