The Corinth Canal is a sea-level ship canal in southern Greece that cuts through the Isthmus of Corinth, linking the Gulf of Corinth, an arm of the Ionian Sea, with the Saronic Gulf in the Aegean. Completed on 25 July 1893, it is about 6.4 km long (6,343 m), only 24.6 m wide at the surface and 8 m deep, with near-vertical rock walls rising up to about 90 m above sea level. It has no locks. By turning the Peloponnese into an island it saves ships a 700 km voyage around the peninsula, but it is too narrow for most modern cargo ships, so its roughly 15,000 transits a year are mostly yachts and tourist boats. What decides whether it is open at all is the Greek weather: wet winters bring down its walls, and the dry season is when boats pass and repairs get done. This guide follows the canal through that year.
December to February on the Isthmus: Rain and Falling Walls
Corinth has a hot-summer Mediterranean climate, and about four fifths of its roughly 463 mm of yearly rain falls between October and March. At the Velo weather station near Corinth, December is the wettest month with about 78.6 mm over about 10 rain days, followed by November (73.5 mm) and January (72.0 mm). January is also the coldest month, with a mean of 9.1 °C. For a trench cut through soft, broken rock, this is the dangerous season.
The canal is cut through heavily faulted sedimentary rock in an active earthquake zone, and its high limestone walls have been unstable from the start. Although the canal was formally opened in July 1893, landslides kept it shut to shipping until November 1894. Between 1893 and 1940 it was closed for a total of about four years so that the walls could be stabilised. The worst single year was 1923, when about 41,000 m³ of rock and soil fell into the channel, and clearing it took two years.
The same pattern returned in the 2020s. At the beginning of 2021, in the middle of the wet season, a landslide closed the canal again. It stayed shut for the rest of that year and well into the next. That closure shows the basic rule of the canal year: winter is when the cutting moves.
March to May: The Dry-Down and the Repair Season
Rain eases through spring, from about 53.7 mm in March to 28.7 mm in April and 22.3 mm in May. Daytime highs climb from 16.5 °C to 25.7 °C. Drier ground and calmer weather are what engineers need to work on the walls, and the canal's reopenings have tended to come at the start of summer.
After the 2021 slide, the canal reopened in June 2022, closed again in October 2022 for further safety work, and reopened on 1 June 2023. The same timing appears in the canal's older history. After German forces blocked it in October 1944, the United States Army Corps of Engineers began clearing it in November 1947. It reopened to shallow-draft boats on 7 July 1948 and to all traffic that September.
Some of the damage comes from the boats themselves. Engineers soon found that the wash from passing ships undermined the base of the walls and set off more slides. The answer was a masonry retaining wall at the water's edge along more than half the canal's length, built with about 165,000 m³ of masonry. They were a further expense for a canal whose traffic was already far below forecasts.
June to August: Five Millimetres of Rain and a Channel of Yachts
High summer is almost rainless. July averages about 5.0 mm of rain on just over one rain day, with a mean temperature of 28.7 °C and average highs of 33.2 °C. This is the canal's busy season, when yachts and tourist boats are on the water and visitors line the road and rail bridges, which cross about 45 m above the water.
Traffic runs one way at a time, in convoys, and larger vessels must be towed by tugs. The water itself is not still. The tides in the two gulfs peak at different times, so a level difference builds up between the two ends and drives a current through the channel. The high walls also funnel wind along its length. Both made early ship operators reluctant to use the canal.
Those tidal currents are small next to what ancient engineers feared. Demetrius Poliorcetes, one of Alexander the Great's successors, dropped his canal plan after his surveyors wrongly calculated that the two seas stood at different levels and warned of heavy flooding. In AD 40 the emperor Caligula commissioned Egyptian experts who made the same mistake, claiming the Gulf of Corinth was higher than the Saronic Gulf and that a canal would drown the island of Aegina. The modern canal was in the end dug at sea level, with no locks at all.
At each end the canal has a bridge that sinks rather than lifts. In 1988 submersible bridges were installed at sea level by the eastern harbour of Isthmia and the western harbour of Poseidonia. When a boat approaches, the roadway is lowered to the canal bed, the vessel passes over it, and the deck rises again for cars.
September to November: Records, Ruin and the Diolkos Repairs
Autumn is a hinge season. September is still dry at about 19.4 mm, but October brings about 40.8 mm and November more than 73 mm, and the slide risk returns. Several of the canal's defining events fell in this window. On 9 October 2019 the cruise ship MS Braemar, 22.5 m wide, 195 m long and carrying up to 900 passengers, became the widest and longest ship to pass through, with barely a metre to spare on each side. In October 2022 the canal closed again for safety work.
The most destructive October came in 1944. As German forces retreated from Greece they set off explosions to bring down the walls, destroyed the bridges, and dumped locomotives and bridge wreckage into the channel. Three years earlier, on 26 April 1941, German glider troops had captured the main bridge, which was then destroyed in an explosion; accounts differ on what set off the charges. Italian army engineers built a replacement rail and road bridge in 25 days.
Autumn was also when work finally began on the canal's ancient neighbour. The Diolkos, a paved trackway for dragging ships across the isthmus, ran close to the modern canal, and wash from passing boats has eroded its excavated western end. Campaigners had petitioned the Greek Ministry of Culture to act, and in October 2024 crews shored up the canal bank where the trackway's edge was crumbling into the water. They also added edging and a separate footpath; by July 2025 the path beside the restored stretch was open.
The Longer Clock: A Widening Rift and a 2,600-Year Plan
Behind the yearly cycle runs a much slower one. The Gulf of Corinth is a tectonic rift that is pulling apart by about 10 mm a year, and its faults can produce earthquakes of up to about magnitude 6.5. In 1858 a magnitude 6.5 earthquake destroyed the old town of Corinth, and a new town was built on the coast to the northeast. A magnitude 6.3 earthquake devastated that new town in 1928, and nearby Loutraki was flattened the same year and shaken again in 1981. The canal is cut through the faulted rock of this same active seismic zone.
The idea of a canal is far older than the canal. Periander, tyrant of Corinth in the 7th century BC, dropped the plan and built the Diolkos instead; it worked from about 600 BC until the middle of the 1st century AD. In AD 67 the emperor Nero broke ground with a pickaxe, and 6,000 Judean prisoners of war dug about 700 m before the work stopped after his death. The modern canal follows Nero's line. After Greece gained formal independence in 1830, Ioannis Kapodistrias had a French engineer assess the idea, which was costed at 40 million gold francs, far beyond the young state's means. The opening of the Suez Canal in 1869 revived it, and a law authorising the canal passed in 1870. King George I inaugurated construction on 23 April 1882 under the Société Internationale du Canal Maritime de Corinthe, headed by István Türr. It ran out of money after eight years and went bankrupt, and a Greek company took over in 1890 and finished the job in 1893. The isthmus it cut is only about 6.3 km wide at that point, a strip that the geographer Strabo described in the 1st century AD as marked by a stone pillar reading "Here is Peloponnesus, not Ionia" on one face.
Traffic never matched the forecasts. Its builders expected almost 4 million net tons a year; by 1906 the canal carried about half a million, and by 1913 about 1.5 million, before the First World War cut it back. Closures, currents and the growth of ships did the rest. For the full story of the dig, read our history of the Corinth Canal; for the weather that sets its calendar, see the climate of Greece; and for the isthmus in its wider setting, explore our map guide to Greece's geography.