THE DIOLKOS AND THE CANAL OF THE ISTHMUS

“The opening of the Isthmus, however, is an eternal task, which is hard to attribute to human efforts, for I think that the cutting through of the Isthmus would require the help of Poseidon and not some mere human being”.

Philostratos, Times of the Sophists, B, VI, 552

                     

       The Diolkos was built because a canal could not be cut, and served as a substitute, as a kind of forerunner to it. The first attempts are recorded in the time of Periandros, Tyrant of Corinth (625-575 BC). He was the first one known to plan the cutting through of the Isthmus. In that epoch trade and navigation had extended to the East and West, and Corinthian products were carried all over the known world. The colonies that had been founded offered safety and protection to the voyagers and provided power, economic, political and naval, to the mother city. Thus Corinth in the era of Periandros was the center of the Hellenic world.

        The two great harbors of Corinth, Lechaion on the Corinthian and Kenchreae on the Saronic Gulf, facilitated the penetration of people, goods and ideas to the East and West. Smaller harbors and trade stations existed along the coastline of the two gulfs.

        Lechaion and Kenchreae were linked by the Diolkos, thus constituting a single functional unit, commercial and military.

        Periandros did not, in the end, carry out his idea of cutting through the Isthmus. The execution of his plan not only encountered engineering and financial obstacles, but also came up against the prevailing religious objections. According to these the gods, and especially Poseidon, to whom the whole area of the Isthmus was sacred, would have been enraged. Moreover, the Pythian oracle at Delphi was opposed to it and dissuaded him from cutting a canal through.

“You must not raise towers on the Isthmus nor dig trenches.

If Zeus had so willed, he would have made [the Peloponnese] an island”

Anonymous, Palatine Anthology, XIV,81

        Almost three centuries passed before Demetrios Poliorketes [Besieger of Cities] (357-283 BC) appeared on the scene. He undertook to cut a canal, in 306BC, through the Isthmus. But he too was dissuaded by his engineers, who expressed their view that cutting through the Isthmus would lead to collapse of part of Aigina and other adjacent small islands. This was believed because the water level of the Gulf of Corinth was thought to be higher than that of the Saronic Gulf. 

“Since the sea on the side of Lechaion was higher, it was feared that Aigina would be covered by the water of the great sea”.

Nero, On the Excavation of the Isthmus, § 639

        In 44BC Julius Caesar (102-44 BC) at the instigation of the Roman Senate, decided to re-found and rebuild Corinth as a colony of Rome, with the name Colonia Laus Julia Corinthiensis. Corinth had for 102 years remained uninhabited after its almost total demolition by the Romans in 146BC. Julius Caesar considered cutting a canal through the Isthmus, but did not get as far as beginning the actual work.

        After Caesar’s death, the emperor Caligula in 37AD tried to restart the work of cutting and constructing a canal through the Isthmus of Corinth, and began the preliminary studies.

These operations were stopped by the violent death of that emperor. And thus was confirmed the saying of Apollo of Thyanea, concerning a canal through the Isthmus, when he visited Corinth:

“The neck of land is not to be cut by anyone at all”

        The many canals that were dug in the Roman world to facilitate trade show a perception of the importance of trade and of its support and promotion by Rome through engineering works, large and small.

        After the accession of Nero to the Imperial throne in 67AD a more serious attempt to pierce the Isthmus began. During his trip through Greece, Nero participated in the Great Isthmian Games. It was here that he took up the idea of cutting through the Isthmus. He himself heralded the commencement of the works with a great ceremony in which he personally sang a hymn to Amphitrite, Queen of the Seas, to their “king” Poseidon, and to the local heroes Melikertes and Leucothea, who were worshipped with special honors at Isthmia.

        Striking the ground with a golden mattock, the Emperor gave the signal to thousands of workmen (Greeks, Romans, Jews), who were lined up along the whole length of the canal to be dug. The last of these groups exceeded 60,000 men, who were taken by Vespasian after he suppressed the uprising in Judea.

“…and a great multitude of men of many nations was taken for this work…”

Dio Cassius LXII, 16.2

 Many of these men were sold as slaves after the work on the canal was halted. It is likely that some were freed and given land in various localities around the Isthmus and were settled in Corinth. Quite a few became tenant farmers, while others labored in the quarries that existed around the Isthmus before they were freed.

“…and there were many others, who required much money…”

Dio Cassius LXII, 17

        The works began with great intensity under the supervision of Nero himself and his engineers.

        They developed synchronously on two fronts, one on the Corinthian Gulf and the other on the Saronic. In all, the excavation opened up trenches more than 2,000m in length, up to 60m wide and with variable depth to 20m.

        From the plans drawn up by the Venetians around the year 1687, it seems that one more trench was opened up, beyond the two main ones. It was approximately perpendicular to the central trough of the Isthmus, and constituted the eastern extension of the great ditch, its length being the greatest of all. These cuttings did not begin at the shore, but at some distance from it. 

        During the final excavation of the canal in 1882, 26 wells or shafts were found of various dimensions with depths of about 20m; many trenches and earthworks were on both sides of the main cutting, which had been made in Nero’s time. A reference to Nero’s trench and shafts can be found in Curtius’ book on the Peloponnese, (1852), p. 546. There is no reference, however, to the Diolkos in particular.

        The works continued unimpeded for two months under Nero’s supervision, until his urgent return to Rome, owing to a rebellion in which most of the Emperor’s provinces took part. The canal works continued for some time, under the supervision of Vaspasian, but definitely ceased, however, after Nero was murdered.

        The digging and building of Nero’s canal along its length would have certainly destroyed parts of the Diolkos, as far as can be seen from many indications. But the Diolkos itself was not destroyed, since it was still used for many centuries after Nero’s attempt to cut through the Isthmus. Measures must have been undertaken to protect it.

        These measures would most likely have been the following:

1) The Diolkos would have been boxed in by supporting walls, or levees, so as to continue operating while the canal was built, because on both sides of the Diolkos a trench quite a few meters deep must have been dug.

2) The trench would not have come close to the embankment of the Diolkos, but would have been well away from it, so that it could still be used. Sections were left within the canal in which the Diolkos existed, without digging.

3) The two sections of the Diolkos next to the Corinthian and the Saronic Gulfs would have been destroyed by the canal works. The Diolkos would have remained unaffected within that interval, as whatever sections of it were destroyed would have been rebuilt, since the canal was not further or fully excavated.

4) The excavation for the canal could have been made away from the course of the Diolkos, without disturbing the level of its setting on the ground surface. The earthworks were entirely on the surface and were made in areas away from the route of the Diolkos.

        The fourth hypothesis above is confirmed in the first section of the Diolkos that which was destroyed by the canal works, near the submersible bridge at Poseidonia. This is attested to by the maps of 1850, which contain a specific reference to the depth of the excavation. Up to a distance of 174m from the shore, there was no digging at all. Beyond the small farmers’ road up to a 390m distance from the shore, digging was done to a depth of 1m. The earthworks from Nero’s diggings must have been located well outside the Diolkos, without halting or disturbing its operation. After completion of the canal’s construction, whatever sections of the Diolkos lay within its zone would have been destroyed because its operation would have been pointless as soon as ships used the finished canal. The so-called “portrait” of Nero at a distance of 1,400m from the Corinthian Gulf entrance of the canal through the Isthmus is one bit of evidence as to at least how far the digging of Nero’s trench had reached. It is likewise evidence of the level to which the canal’s excavation went. The base of the image marks the least depth of excavation there below the initial ground surface.

        The representation is essentially a relief sculpture depicting Heracles with his club and his lion’s skin and head, regarded more generally as the protector of working men, and thus also of those who worked on the canal.

        After Nero, Herodes Atticus tried to continue the work, but very soon abandoned it. During the later centuries, until the second period of Venetian rule, nothing changed. Then, in 1687, the Venetians thought of cutting a canal through the Isthmus, beginning from the Gulf of Corinth. But this idea was never realized because of economic problems, technical obstacles, and their brief stay on the Peloponnese. After the Venetians, there are no further references to attempts at cutting through the Isthmus. Just after the founding of the present Greek state, Count Capodistrias, its first [and only] Governor, thought of opening a canal here, a project that was then entirely excluded by its high estimated cost. The work finally began after many legal proceedings and inquiries on 22 April 1882, and was completed in 1892. The initial studies envisaged a canal 44m wide at sea level, and a declivity [of its banks] sloping with a gradient of 1:5, and their stepped configuration. This stepped configuration was to prevent crumbling and collapse of the banks into the canal.