From the Wikipedia: Kaunos (Carian: Kbid; Lycian: Khbide; Ancient Greek: Καῦνος; Latin: Caunus) was a city of ancient Caria and in Anatolia, a few km west of the modern town of Dalyan, Muğla Province, Turkey.
The Calbys river (now known as the Dalyan river) was the border between Caria and Lycia. Initially Kaunos was a separate state; then it became a part of Caria and later still of Lycia.
Kaunos was an important sea port, the history of which is supposed to date back till the 10th century BC. Because of the formation of İztuzu Beach and the silting of the former Bay of Dalyan (from approx. 200 BC onwards), Kaunos is now located about 8 km from the coast. The city had two ports, the southern port at the southeast of Küçük Kale and the inner port at its northwest (the present Sülüklü Göl, Lake of the Leeches). The southern port was used from the foundation of the city till roughly the end of the Hellenistic era, after which it became inaccessible due to its drying out. The inner or trade port could be closed by chains. The latter was used till the late days of Kaunos, but due to the silting of the delta and the ports, Kaunos had by then long lost its important function as a trade port. After Caria had been captured by Turkish tribes and the serious malaria epidemic of the 15th century AD, Kaunos was completely abandoned.
The oldest find at the Kaunos archeological site is the neck of a Protogeometric amphora dating back to the 9th century BC, or even earlier. A statue found at the western gate of the city walls, pieces of imported Attic ceramics and the S-SE oriented city walls show habitation in the 6th century BC. However, none of the architectural finds at Kaunos itself dates back to earlier than the 4th century BC.

On many images taken from the acropolis you will see pictures of the river and further on Dalyan, a delightful town at the river. A short walk in the other direction will bring you to Çandır village and a small private museum.