It was built by Kaunos, one of the twin children of Miletus, and is on the UNESCO World Heritage Tentative List under the name of Kaunos Ancient City. Kaunos hosted settlements from the archaic, classical, Hellenistic, Roman and Byzantine periods. Today, the magnificent delta and city view of Dalyan, within the borders of Ortaca district, can be seen from the ancient city castle in Köyceğiz's Çandır District.

According to Herodotus, the father of history, the people of Caunos were one of the ancient peoples of Caria, but they called themselves Cretans. Geographer Strabo wrote that Kaunos had a shipyard and a retractable harbour.

Kaunos was an important trade city of ancient times. The city's port was located below the acropolis, in what was once Sülüklü Lake, but over time, the old knowledge of Kaunos was lost as the port entrance was closed by alluviums. At that time, the sea reached the acropolis of Kaunos, and today it is located on a hill 152 meters above sea level. There are also ruins of a theater with 33 rows of seats, a basilica-type church, a Roman bath and a temple in the city.

Demeter, the future of abundance and abundance, was important in the world of belief in Kaunos, and in her name, there were three days of "Fertility Festival" every year, attended only by women.

The rock tombs carved into the rocks with a view of Dalyan differentiate Kaunos from other ancient cities. The rock tombs with temple facades, first seen in Kaunos, are different from the rock tomb facade architecture in the Urartian, Phrygian and Lycian regions. With its unique appearance, it reflects the façade architecture of the Hellenic Temple and is far from other rock tomb types. On the right side of the rocks, six temple-type tombs are carved into the rocks with the fineness of a sculptor. Rock tombs have been mute rumors of the past ever since, with 2,400 letters throughout their lives... The secret of the King's Tombs, which can be seen from the Dalyan River, is the belief in ancient times that the higher or closer the tombs were.