The Corinth Canal
The Isthmus of Corinth is a narrow strip of land that connects Central Greece with the Peloponnese. It is about 6 kilometers long and the narrowest point is where the Corinth Canal was built (1880-1893), which technically makes the Peloponnese an island. Today two highways, two railways and two submerged bridges at the two ends of the canal connect the mainland of the Isthmus with that of the Peloponnese.
(83 km away)