Iasos was founded by colonists from Argos and later came under the control of Miletus in the 5th century B.C. The city was a member of the Attica-Delos confederation. Many citizens of Iasos earned their livelihood from fishing, a tradition that continues today. Apollo and Artemis served as the protective deities of the city. Like other settlements in the region, Iasos was destroyed by the Persians.
The ancient city regained its importance during the era of Alexander the Great. Gorgos of Iasos was one of Alexander's distinguished commanders. Together with his brother, Gorgos developed the fishing industry in Iasos. In gratitude, the citizens erected statues of both brothers in the theatre and exempted them from paying taxes for the rest of their lives.
For boys who completed their daily training at the gymnasium in Iasos, swimming in the sea was a cherished tradition. According to legend, while the boys were bathing, a dolphin would take one particular boy for rides around the bay. Alexander the Great later appointed this boy as a priest in Babylon. Another legend tells of a tragic accident where the boy was wounded while playing with the dolphin. The dolphin carried the dying boy to shore and died beside him on the beach. Ancient coins depicting a boy riding a dolphin date from the 3rd century B.C.
Today, visitors can explore the well-preserved agora, the theatre with its impressive ashlar masonry dating from the 4th century B.C., the bouleuterion, the temple dedicated to the goddess Artemis, the ancient fish market, and a funerary monument resembling a Corinthian temple from the Roman period.