In ancient times ships of small burden were regularly dragged on rollers or waggons across the narrowest part of the Isthmus in order to avoid the long voyage round Peloponnese; hence this part of the Isthmus was known as the _Diolkos_ or Portage. The Portage began on the east at Schoenus, near the modern Kalamaki; its western termination is not mentioned by ancient writers, but was probably near the west end of the modern canal. We read of fleets of warships being transported across the Isthmus; for example after the battle of Actium the victorious Augustus thus conveyed his ships across the Isthmus in pursuit of Antony and Cleopatra, and in 883 A.D. the Greek admiral Nicetas Oriphas transported a fleet across it to repel an attack of the Saracens. Some remains of the ancient Portage, which seems to have been a sort of tramway, may still be seen near a guard-house, at the point where the road from Kalamaki to Corinth crosses the northern of the two ancient fortification walls. The lowest and narrowest part of the Isthmus, through which the Portage went in antiquity and the modern canal now runs, is bounded on the south by a line of low cliffs. Along the crest of these cliffs may be traced the remains of an ancient fortification wall stretching right across the Isthmus from sea to sea. It is built of large blocks laid in fairly regular courses, and is flanked by square towers which project from the curtain at regular intervals of about a hundred yards on the north side, showing that the wall was meant to protect the Corinthian end of the Isthmus against invasion from the north. The wall does not extend in a straight line, but follows the crest of the cliffs, wherever this natural advantage presented itself.