Kas was originally called Habesos or Habesa in the ancient tongue of Lydia and later was given the name Antiphellos. It is one of the oldest settlements in the region of Lydia. Most of the ancient settlement is now covered by the modern town of Kas. The rock-cut tombs to the northeast of the town date to the 4th century BC
On a rise between the open sea and the hill, which was probably the acropolis of the ancient city, lies a rock tomb formed like a Doric structure with Doric triglyphs on the facade. Inside the tomb is to be found a frieze of dancing female figures.
The acropolis was surrounded by a fortified wall, of which traces are to be seen on the facade facing the island of Meis (Kastellorizon). No traces of fortifications are to be seen on the northern or western slopes. To the west of the modern town stands the ancient theater overlooking the sea.
This structure possesses a remarkable view. It was constructed of local limestone and today the tribunes and outer walls are still visible although no trace of the skene is left. On the western edge of the acropolis are traces of a temple. Tombs of the Roman Period are scattered about the town and along the coast.