This is the other end of the tunnel that was dug under the Roman emperors Titus and Vespasian. Vespasian reigned until 79, then his son Titus took over. The purpose of the complex was to shunt off water that might flood the city that now is Çevlik and formerly was Seleucia ad Piera.

To the right you can see the inscription memorating the feat.

I utterly forgot to continue my walk, and arrive at some rock graves from the period. I saw pictures of them: not spectacular, but nice enough to be woirth that walk.