The ancient city of Seleucia ad Calycadnum stretched along the slopes of the fortress hill. The river banks and the Göksu estuary have been inhabited since the early Bronze Age. According to the latest archaeological research, the earliest settlement discovered can be equated with the Hittite era, which dates back to the 13th century BC. In 712 BC, the Assyrian king Sargon II fortified Ura for the first time. Seleucos I. Nikator, one of the generals Alexander the Great and later king of the new kingdom of Babylonia (Syria) must have renamed the existing settlement Seleukeia. The number of cities named after Seleukos is 9. Seleucia ad Calycadnum is the only one that - today under the name Silifke - shows an intact cityscape. All the others are now ruin fields.

After Stephen of Byzantium was the old name of Seleukeia Huria. The American archaeologist William Foxwell Albright equates Silifke with the Luwian Ura.

Under the Romans Seleukia (lat. Seleucia ad Calycadnum) became the capital of Isauria. In the Middle Ages, the city was temporarily the capital of the Kingdom of Little Armenia.
Emperor Friedrich Barbarossa drowned in 1190 on the Third Crusade near the city in Göksu, which at that time was called Saleph.

The fortress of Silifke (Turkish: Silifke Kalesi) is the ruin of a medieval castle on a hill above the town. The fortress is situated on a hill, about 160 m above sea level, above the Göksu River, the ancient Kalykadnos, on the western outskirts of the city. It thus served to control the road leading west from Cilicia and the road leading north along the Kalykadnos over the Taurus.

The interior of the fortress

Today's ruins are mostly of Byzantine origin with Armenian influences. The castle has a surrounding, partly preserved, partly restored crenellated wall with formerly 23 towers, which was surrounded by a moat. The main entrance is in the north. Farm and residential buildings inside were grouped around an open courtyard. The visible, heavily overgrown remains include a palace ruin, a pantry, a cellar dungeon, a cistern and a mosque.

On the Inönü Caddesi in today's Silifke lies one of the few remains from Roman times.
The building was a peripteral temple with 14 columns on the long side and eight on the front. The dimensions are 40 × 21 metres. Today only parts of the podium and a fluted column carrying a Corinthian capital as well as scattered column drums are preserved. Parts of the gable or the bellow are not preserved, only a fragment of a frieze with garlands and a representation of St. Nicholas can be found in the Silifke Museum.
The temple was built in the Roman imperial period in the 2nd century.
To which deity the temple was dedicated is unknown. It could be the Temple of Zeus, which was converted into a basilica in the 5th century. According to another interpretation, it was a temple of Apollo Sarpedonicus or the temple of Aphrodite, which was transformed into a church in the first half of the 5th century under Bishop Dexianos.

Byzantine cistern

On the way to the fortress there is a cistern built in early Byzantine times. It was carved into the rocks on a terrace of the mountain slope. It is rectangular, the east-west oriented long sides measure 46 meters, the narrow sides 23 meters, the depth of the building is about 12 meters.
The side walls form arches of ashlar masonry, eight each on the long and five on the short sides with remains of bricks on the walls. The tributary was in the northwest. On the east side there is a spiral staircase which is still accessible today and leads into the interior.
There are also arches for arches to freestanding columns in the interior, which were either planned or dismantled as spoils. From this it can be concluded that a roofing of the cistern was at least in planning. The British captain Francis Beaufort, who explored the Cilician coast on behalf of the Admiralty in 1811-12, mentions the cistern in his report and also describes a ceiling construction.