Selinus is the ancient port above Gazipasa's river mouth, with ruins scattered across the hill and flat ground behind the beach. Do not expect the neat presentation of Ephesus or Side; this is rougher, quieter, and more atmospheric, with the Mediterranean below and the Taurus Mountains behind.
The site is best combined with Selinus Beach. Wear shoes with grip if you climb toward the hilltop remains, and avoid the hottest part of the day. The lack of crowds is a gift, but it also means less shade, less signage, and fewer services.