The Diolkos—from the Greek dia (across) and holkos (portage)—was a paved trackway in Ancient Greece which enabled boats to be moved overland across the Isthmus of Corinth. The short cut allowed ancient vessels to avoid the dangerous circumnavigation of the Peloponnese peninsula.
The main function of the Diolkos was the transfer of goods, although in times of war it also became a preferred means of speeding up naval campaigns. The to long roadway was a rudimentary form of railway, and operated from ca. 600 BC until the middle of the 1st century AD. The scale on which the Diolkos combined the two principles of the railway and the overland transport of ships remained unique in antiquity.
saved ships sailing from the Ionian Sea
to the Aegean Sea
a dangerous sea journey round the Peloponnese, whose three headlands had a reputation for gales, especially Cape Matapan
and Cape Malea
. By contrast, both the Gulf of Corinth
and the Saronic Gulf
were relatively sheltered waters. In addition, the overland passage of the Isthmus, a neck of land wide at its narrowest, offered a much shorter route to Athens
for ships sailing to/from the Ionian coast of Greece.
Ancient literature is silent on the date of the construction of the Diolkos. For Thucydides
(460 BC–395 BC) the Diolkos already seemed to be something ancient. Excavated letters and associated pottery found at the site indicate a construction date at the end of the 7th
or beginning of the 6th century BC, that is around the time when Periander
was tyrant of Corinth
. The Diolkos remained reportedly in regular service until at least the middle of the 1st century AD, after which no more written references appear. Possibly the trackway was put out of use by Nero
's abortive canal works in AD 67. Much later transports of warships across the Isthmus in the late 9th century and around 1150 are not assumed to have been on the Diolkos due to the extensive time lag.
Role in warfare
The Diolkos played an important role in ancient naval warfare. Greek historians note several occasions from the 5th
to 1st century BC when warships were hauled across the Isthmus in order to speed up naval campaigning. In 428 BC, the Spartans
planned to transport their warships over the Diolkos to the Saronic Gulf to threaten Athens
, while later in the Peloponnesian War they carted over a squadron heading quickly for operations at Chios
(411 BC). In 220 BC, Demetrius of Pharos
had a fleet of about fifty vessels dragged across the Isthmus to the Bay of Corinth by his men. Three years later, a Macedonian
fleet of 38 vessels was sent across by Philip V
, while the larger warships sailed around Cape Malea. After his victory at Actium
(31 BC), Octavian
advanced as fast as possible against Marc Antony
by ordering part of his 260 Liburnians
to be carried over the Isthmus. In AD 868
, the Byzantine
admiral Niketas Oryphas
had his whole fleet of one hundred dromons
dragged across the Isthmus in a quickly executed operation, but this took place most likely on a different route.
Role in commerce
Despite the frequent mentioning of the Diolkos in connection with military operations, modern scholarship assumes that the prime purpose of the trackway must have been the transport of cargo, considering that warships cannot have needed transporting very often, and ancient historiography was always more interested in war than commerce. Comments by Pliny
who described in times of peace the Diolkos as being in regular service also imply a commercial use of the trackway. Coinciding with the rise of monumental architecture in Greece
, the construction of the Diolkos may have initially served particularly for transporting heavy goods like marble
to points west and east. It is not known what tolls Corinth
could extract from the Diolkos on its territory, but the fact that the trackway was used and maintained long after its construction, indicates that it remained for merchant ships an attractive alternative to the trip around Cape Malea for much of antiquity.
The Diolkos runs across the narrowest part of the Isthmus, where the trackway followed the local topography in a curved course in order to avoid steeper gradients. The roadway passes the Isthmus ridge at ca. height with an average gradient of 1:70, while the steepest sections rise up to 6%. Its total length is estimated at 6–7 km (3.7–4.3 mi), or depending on the number of supposed bends taken into account. A total of has been archaeologically traced, mainly at its western end close to the bay of Corinth. There the known trackway begins at a mooring place south of the canal, runs parallel to the waterway for a few hundred meters, after which it switches to the north side, running in a slight bend a similar distance along the canal. From there on, the Diolkos either followed in a straight line the course of the modern canal, or swung south in a wide arc. The roadway ended at the Saronic Gulf at the village Schoinos (today: Kalamaki) described by Strabo as eastern terminal. Some sections of the Diolkos have been destroyed by the 19th century canal or other modern installations.
Track and transport
The Diolkos was a trackway paved with hard limestone and parallel grooves running about apart. The roadway was to wide. Since ancient sources tell us little about how the ships were hauled across, the mode of ship transport has largely to be reconstructed from the archaeological evidence. The tracks indicate that transport on the Diolkos was done with some sort of wheeled vehicle. Either vessel and cargo were hauled across on separate vehicles, or only the cargo was taken across and reloaded on a different ship at the other side of the Isthmus. It is assumed that the vessels were usually rather boats than ships, although a technical analysis has shown that the transport of Triremes (25 t, 35 m (115 ft) long, 5 m (16 ft) beam) was technically feasible, but difficult. To prevent the danger of breaking the keel in middle during transport, hypozomata must have been used which were thick ropes running from bow to stern meant to reduce sagging and hogging of the hull. Ship and cargo were presumably pulled by men and animals with the help of ropes, tackles and possibly also capstans.
The scientist Trolley aimed at establishing the manpower which was necessary for hauling the vessels over the Isthmus ridge: Assuming that a Trireme soaked with water weighed 38 t including its trolley, and that a man can exert a force of 300 N over a longer period of time, the pulling teams - depending on the slope and the surface of the cat track - must have numbered between 112 and 142 people (33 550 to 42 500 N). Bringing the trolley up to speed would have even required 180 men. With 2 km/h speed over an estimated length of 6 km, the transfer process from sea to sea would have thus taken three hours to complete.
Assuming less load and rolling friction, Raepsaet, in contrast, calculates a maximum pulling force of 27 000 N, which would have resulted in a significantly smaller towing crew. Under these circumstances, the use of harnessed oxen - which has been refuted by Trolley on the basis of their relatively dimishing pulling capabilities - would have become feasible. In any case, the necessary expenditure of energy at the Diolkos must be regarded in both scenarios as considerable.
According to the British historian of science M.J.T. Lewis, the Diolkos represented a railway
, in the basic sense of a prepared track which so guides the vehicles running on it that they cannot leave the track. Measuring between and , remaining in regular and frequent service for at least 650 years, and being open to all on payment, it constituted even a public railway, a concept which according to Lewis did not recur until around 1800. Also, its average gauge
of around is similar to modern standards.
However, a close examination of the excavated tracks may give a more differentiated picture. While there is agreement that the grooves in the eastern part were cut deliberately into the stone slabs to guide cart wheels, those in the western section are interpreted by some authors as a result of wear or do not appear at all. On the other hand, the marked cambers of this road section may point at deliberate tracks as well. Generally, varying forms of the grooves can also be explained with the long time of operation of the trackway during which modifications and repairs must have significantly changed the appearance of the Diolkos.
The chief engineer of the Corinth Canal Béla Gerster
conducted extensive research on the topography of the Isthmus, but did not discover the Diolkos. Remains of the ship trackway were probably first identified by the German archaeologist Lolling in the 1883 Baedeker
edition. In 1913, J.G. Frazer reported in his commentary of Pausanias
on traces of an ancient trackway across the Isthmus, while parts of the western quay were discovered by Fowler in 1932.
Systematic excavations were finally undertaken by the Greek archaeologist Nikolaos Verdelis between 1956 and 1962, who uncovered a more or less continuous stretch of and traced about in all. Even though Verdelis’ excavation reports continue to provide the basis for modern interpretations, his premature passing prevented full publication, leaving many questions open concerning the exact nature of the structure. Additional investigations in situ, meant to complement Verdelis’ work, were later published by Georges Raepsaet and Walter Werner.
Today, erosion caused by ship movements on the nearby Canal has left considerable portions of the Diolkos in demolition, particularly at its excavated western end. Critics who blame the Greek Ministry of Culture
for continued inactivity have launched a petition for saving and restoring the registered archaeological site.
The following ancient writers mention the transfer of ships across the Isthmus (in chronological order):
- Thucydides 3.15.1, 8.7, 8.8.3–4
- Aristophanes, Thesmophoriazusae 647–648
- Polybius 4.19.7–9 , 5.101.4 , frag. 162 (ed. M. Buettner-Wolst)
- Livy 42.16.6
- Strabo 8.2.1 [C.335], 8.6.22 [C.380], 8.6.4 [C.369]
- Pliny, Natural History, 4.9–11, 18.18
- Cassius Dio 51.5
- Hesychius (ed. Schmidt, I, p. 516.80)
- Suidas 2.92
- George Sphrantzes 1.33
- Joubert, P.A.: Géographie d'Édrisi 2 (Paris 1840), p. 123
- Cook, R. M.: "Archaic Greek Trade: Three Conjectures 1. The Diolkos", The Journal of Hellenic Studies, Vol. 99 (1979), pp. 152–155
- Drijvers, J.W.: "Strabo VIII 2,1 (C335): Porthmeia and the Diolkos", Mnemosyne, Vol. 45 (1992), pp. 75–76
- Lewis, M. J. T., "Railways in the Greek and Roman world", in Guy, A. / Rees, J. (eds), Early Railways. A Selection of Papers from the First International Early Railways Conference (2001), pp. 8–19 (10–15)
- MacDonald, Brian R.: "The Diolkos", The Journal of Hellenic Studies, Vol. 106 (1986), pp. 191–195
- Raepsaet, G. & Tolley, M.: "Le Diolkos de l’Isthme à Corinthe: son tracé, son fonctionnement", Bulletin de Correspondance Hellénique, Vol. 117 (1993), pp. 233–261
- Verdelis, N. M.: "Der Diolkos am Isthmus von Korinth", Mitteilungen des deutschen Archäologischen Instituts, Athenische Abteilung, Vol. 71 (1956b), pp. 51–59
- Verdelis, N. M.: "Die Ausgrabungen des Diolkos während der Jahre 1957–1959", Mitteilungen des deutschen Archäologischen Instituts, Athenische Abteilung, Vol. 73 (1958), pp. 140–145
- Werner, Walter: "The largest ship trackway in ancient times: the Diolkos of the Isthmus of Corinth, Greece, and early attempts to build a canal", The International Journal of Nautical Archaeology Vol. 26, No. 2 (1997), pp. 98–119