The Isthmus of Corinth is the narrow land bridge which connects the Peloponnese peninsula with the rest of the mainland of Greece, near the city of Corinth. The word “isthmus” comes from the Ancient Greek word for “neck” and refers to the narrowness of the land. The Isthmus was known in the ancient world as the landmark separating Peloponnese from mainland of Greece. In the first century CE the geographerStrabo noted a pillar on the Isthmus of Corinth, which bore two inscriptions. One towards the East, i.e. towards Megara in Attica reading: “Here is not Peloponnesus, but Ionia” (τάδ᾽ οὐχὶ Πελοπόννησος, ἀλλ᾽ Ἰωνία) and the one towards the West, i.e. towards the Peloponnese: “Here is Peloponnesus, not Ionia” (τάδ᾽ ἐστὶ Πελοπόννησος, οὐκ Ἰωνία); Plutarch ascribed the erection of the stele to the Attic hero Theseus, on his way to Athens. 
To the west of the Isthmus is the Gulf of Corinth, to the east the Saronic Gulf. Since 1893 the Corinth Canalhas run through the 6.3 km wide isthmus, effectively making the Peloponnese an island. Today, two road bridges, two railway bridges and two submersible bridges at both ends of the canal connect the mainland side of the isthmus with the Peloponnese side. Also a military emergency bridge is located at the west end of the canal.