The Isthmus of Corinth is the strip of land that joins the Peloponnese to the rest of Greece. It is only about six kilometres wide, but it separates two seas. Before the canal was cut, a ship going from one to the other had to sail all the way around the Peloponnese. That is why, for two and a half thousand years, people wanted to cut through it.
The Corinth Canal does exactly that. It joins the Gulf of Corinth, on the Ionian side, with the Saronic Gulf, on the Aegean side, and it saves ships the long passage around the Peloponnese. It runs in a straight line for 6,346 metres, is 24.6 metres wide at the surface and about eight metres deep, and it was cut at sea level, so it needs no locks. Its limestone walls rise almost vertically to around ninety metres above the water. Standing on the road bridge and looking down at a ship passing between them is the reason most people stop here.
Two and a half thousand years of trying
Periander, the ruler of Corinth in the seventh century BC, was the first to consider cutting the isthmus. He decided it was beyond him and built the Diolkos instead — a paved trackway on which ships were dragged overland from one gulf to the other. It worked for centuries.
The Roman emperor Nero actually began. In AD 67 he started the work with Jewish prisoners taken in the Jewish war, and the digging advanced more than three kilometres before he was called back to Rome to face a revolt. He died soon after and the work stopped. When the modern canal was cut, the engineers found twenty-six of Nero's test shafts, each ten metres deep — and the modern channel follows almost exactly the line he had chosen. A relief of Heracles carved into the rock during his attempt survives.
The Byzantines took a different view of the isthmus: they walled it. The Hexamilion ran from one sea to the other, about seven kilometres, to keep invaders out of the Peloponnese.
The canal that was built
Work finally began in 1882, to a design by the Hungarian engineers István Türr and Béla Gerster. The French company running it went bankrupt, a Greek firm took over in 1890, and the canal opened on 25 July 1893. The two small towns at either end, Isthmia and Poseidonia, were built in 1884 to house the workers.
It has never been an easy waterway. The walls slide. Landslips closed it for a total of four years before 1940, and in 1944 the retreating Germans blew up the sides and dumped railway wagons into the channel; clearing it took five years. It closed again in January 2021 after further collapses, and returned to full operation for shipping on 17 June 2026, after major works to stabilise the slopes.
It is also too narrow for modern cargo ships. Most of the traffic through it now is tourist boats and small vessels.
What to see
The road bridge on the old national road crosses about forty-five metres above the water and is the classic viewpoint. There is parking, cafés and a shop beside it.
The submersible bridges are the surprise. Installed in 1988 at each end of the canal, at Isthmia and Poseidonia, they carry the road at sea level — and when a ship comes through, the whole bridge sinks under the water and then rises again afterwards. It is worth timing a visit to see one operate.
Boat trips run through the canal from Isthmia, taking about an hour, and the scale of the cut is completely different from below.
The Diolkos survives in sections near the western end. You can see the paved surface and the grooves cut for the wheels. Part of it lies underwater at Poseidonia.
At Isthmia, on the eastern side, are the remains of the sanctuary of Poseidon and the site of the Isthmian Games, one of the four great athletic festivals of the Greek world, with a small museum.
