Iassos is an ancient Carian site located around Gulluk Gulf in the Aegean Sea, around 85 km (53 mi) north of Bodrum and 28 km (17 mi) from Milas, in Mugla province. The site can be reached by road, or a nice boat ride from Gulluk town across the gulf. Originally the city was located on an island, but now is connected to the mainland due to silting up since centuries in order to form a peninsula. Scientific excavations in the site started in 1960 by Italian archaeologists. Some of the artifacts found at the site are displayed in the archeological museum in Izmir.

Its history dates back to the mid-Bronze Age, about 3rd millennia BC. Later on it was a colonial foundation of Argos in Asia Minor, then became a member of the Delian League around 5th century BC. Iassos was ruled by the Persians until 4th century BC when it was conquered by Alexander the Great, and then by the Romans and Byzantines. The city was abandoned around 15th century during the Ottoman period.

Iassos was a celebrated fishing place and trade in fish with its two harbors in the ancient times, but most important of all it was famous for its unique marble type; a purple and blood-red one with strong white veins. This marble was exported to all over and used for ornamental purposes in the buildings, such as in Hagia Sophia in Istanbul.

Some of the important buildings of the site are the acropolis on the highest point of the city, the breakwater tower at the western harbor, a well-preserved bouleterion, a theater with many rows of seats, agora (marketplace) surrounded by porticoes and temples, temple of Artemis (Diana), necropolis, a Roman residence with floor mosaics, and a Roman funerary monument from 2nd century AD with a large courtyard of 40 x 48 meters (131 x 157 feet) which today is named as Fish Market by locals. There are also ruins of the walls surrounding the ancient city, as well as fragments of aqueducts.

Besides Iassos site you may like to pay a visit to Euromos site nearby.