You do not need old maps to find it. If you arrive from Athens by road, you cross the boundary without noticing: a high bridge, a couple of seconds looking down, and you are on the "island". If you do not look down, nothing tells you that you have just crossed a canal.

A narrow, straight canal between two tall walls of pale rock seen from a bridge; in the distance another bridge spans the canal under a clear sky.
The Corinth Canal from one of its bridges: 6.3 km of straight cut, with the water at the bottom of a gorge.Elgaard / CC BY-SA 4.0·CC BY-SA 4.0

01 A six-kilometre cut through a rock gorge

The Corinth Canal is 6,343 metres long. It is 24.6 metres wide at the surface and 21.3 at the bottom, and was dug about 8 metres deep, at sea level and with no locks. The walls are nearly vertical and, depending on the source, rise between roughly 80 and 90 metres above the water: it is a gorge, not a ditch.

The reason is plain nautical geography. Without the canal, a ship going from the Gulf of Corinth to the Aegean must go all the way round the Peloponnese, a detour of about 700 kilometres. With the canal, it crosses the isthmus in a short run of a few minutes. The work exists to save that detour.

The sources agree on the essentials, that the canal separates the Peloponnese from the mainland, but describe it as a "peninsula" out of habit. Several note that, technically, it is already an island; what is missing is the habit of saying so, as with other peninsulas cut off from the rest by an artificial waterway.

02 Before the canal, ships crossed overland

The canal was not the first solution. Around the 7th to 6th century BC the Diolkos was built on the same isthmus: a paved limestone road roughly 3.4 to 6 metres wide and about 6 kilometres long, along which ships and cargo were dragged from one gulf to the other. Sources disagree on the exact date and on how it worked, but agree on the basics: grooves and a recognisable line survive, and it was used for centuries.

A stretch of stone paving almost covered by dry grass and small flowers beside a calm shore; a breakwater and low hills lie behind.
Remains of the Diolkos trackway on the isthmus shore: worn stone beneath the grass, a few metres from the sea.Davide Mauro / CC BY-SA 4.0·CC BY-SA 4.0

One fact sums it up. Around 217 BC, according to ancient sources cited in modern studies, Philip V of Macedon sent 38 warships across it. For centuries, in other words, the isthmus was crossed by hauling ships overland, and that effort was judged more practical than sailing round the Peloponnese.

Cutting the rock was also tried. Nero opened a trench in AD 67; according to Suetonius it reached about 700 metres before the work stopped at his death. It took almost eighteen centuries to try again.

A wide pale gravel path between two mounds of yellow earth, with palm trees on the right and a sign beside a stone wall; water shows between trees in the background.
The end of the Diolkos on the Gulf of Corinth side, as seen at the archaeological site.George E. Koronaios / CC0·CC0

03 Eleven years of work for a canal born narrow

The modern work began in 1881; it was formally inaugurated on 23 April 1882 and finished on 25 July 1893, after about eleven years. The Hungarian engineers István Türr and Béla Gerster led the project; the original company ran into financial trouble and a Greek company headed by Andreas Syngros ended up taking over. Popular sources mix up dates and roles, so it is best to hold to what agrees: more than a decade and a change of hands.

Old sepia-toned photograph of a very deep cut between two rock walls, with rails on the ground, an excavating machine on the right and a group of small figures in the distance; a metal bridge spans above.
Period photograph, around 1890, of the canal works: the walls are already very tall and the floor is still full of rails and machinery.Unknown author / Public domain·Public domain

The canal was built for the ships of its day, which explains a problem that was never solved. Nearly 4 million net tons a year were expected; in 1906 half a million was reached and in 1913, a million and a half. Between 1893 and 1940 it was closed for about four years in total to stabilise the walls, which kept shedding rock. And with 24.6 metres as the maximum beam, it is today too narrow for most modern shipping.

04 What happens today with a pocket-sized island

Today about 15,000 ships a year pass through, some 40 a day, and most are tourist vessels. It is no longer a heavyweight trade route: it is an attraction and a piece of infrastructure that is kept up. The limit for a ship is 24.6 metres of beam, 7.3 of draft and 52 of height above the water; the length record was set in 2019 by the cruise ship Braemar.

A small cargo ship moving along a very narrow canal between two tall rock walls; a metal bridge spans the canal in the distance.
A vessel being tugged through the canal: the hull takes up almost the whole width of the water.FocalPoint / CC BY-SA 3.0·CC BY-SA 3.0

Landslides remain part of the story. The canal closed in early 2021 after a slide, reopened in June 2022, closed again a few months later and did not reopen until 1 June 2023, with new safety measures. In 1988 two submersible bridges were installed, one at each end, giving two more road crossings at sea level; the railway, a road and the motorway cross it overhead, at about 45 metres.

05 How to cross without noticing, and how to notice

The Peloponnese is hard to understand without that cut. It is why, coming from Athens by land, you enter through Corinth, and why the isthmus is a narrow crossing point, with road, rail and canal squeezed into a few kilometres. Looking at the canal is looking at why the Peloponnese has always been so close to the mainland and yet so separate.

What to do with this
  1. Stop at the bridge, do not drive past
    The best way to see the canal is from one of the bridges over the cut. If you drive, find a parking spot near the end of the bridge and look down: the width makes sense the moment you see it.
    the spot
  2. See both ends
    On the Gulf of Corinth side, the Diolkos site lets you see the stone road and its grooves. With canal and trackway in the same afternoon, you see how the same problem was solved in two eras.
    two eras
  3. The submersible bridges are a trick, not a flaw
    At both ends there are two bridges that sink under the water to let ships through. If you have to wait, it is the canal working, not a road closure.
    at sea level
  4. Check the canal's status
    It was closed by landslides in 2021 and 2022 and reopened in June 2023. Before organising a boat trip that depends on crossing it, check whether it is operating.
    before you go

The practical conclusion is a modest one: you need no passport stamp and no postcard island to be on an island. It is enough to look up when you cross the Corinth bridge and remember that below you, some forty-five metres down, Aegean water is meeting the water of the Gulf of Corinth.

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Lucía Montes

Worth Knowing editor · Flowtravel

Lucía Montes chases the fact that changes how you look at a place, and follows it through.

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