Korinth (Corinth) Canal, Greece
The Corinth Canal in Greece is an incredible feat of engineering and was once an important navigational route which allowed ships to enter the Aegean Sea.
Carved through the isthmus at sea level, the canal is 6.4 km long with a width of only 25 metres. Impossible for modern ships to go through, the canal has now lost any significant economic importance that it once had.
It is actually one of the longest, if not the longest, construction project in history with initial work starting 300 BC and the actual canal being finally finished in 1893 after many aborted attempts.
Today it is traversed by road & rail bridges, connecting the Peloponnese with the rest of the mainland.