The scant ruins of Seleuceia in Pieria at Çevlik, Antioch's port in ancient times 5km northwest of Samandağ, are hardly impressive, but they include the Titus & Vespasian Tunnel, an astonishing feat of Roman engineering. Seleucia lived under the constant threat of flooding from a stream that descended from the mountains and flowed through the town. To counter this threat, 1st-century Roman emperors Titus and Vespasian ordered that a 1.4km-long channel be cut through the solid rock to divert the stream.
From the gişe (ticket kiosk), follow the trail along an irrigation canal and past some shelters cut into the rock, finally arriving at a Roman arch spanning the gorge and the entrance to the tunnel. Bring a torch as the path can be slippery. At the far end of the channel an inscription provides a date for the work carried out by sailors and prisoners from Judea. About 100m from the tunnel are a dozen Roman rock tombs with reliefs, including the excellent Beşikli Mağarası (Cave with a Crib).