The city of Corinth is located about two miles south of the narrow isthmus which forms the land bridge, and controlled access, between the main land mass of Greece and the Peloponnesus.
The isthmus is less than five miles wide. In ancient times small ships were dragged across the isthmus on a paved road called the diolkos. Small portions of the diolkos may still be seen. Larger ships unloaded their cargo which was carried across and reloaded. This avoided the long 200 mile journey around the Peloponnesus. Nero abandoned his attempts to dig a canal across the isthmus (A. D. 67).
A canal was constructed between 1881 and 1893. Here is a photo of that canal with a tug boat pulling a ship through the canal.
The apostle Paul likely came to Corinth about A.D. 51, during the reign of the Roman Emperor Claudius, and remained there for eighteen months (Acts 18). The book of Acts records the success of that work:
Crispus, the leader of the synagogue, believed in the Lord with all his household, and many of the Corinthians when they heard were believing and being baptized. (Acts 18:8).
Archaeological excavations have been conducted at the ancient city of Corinth since 1896 by the American School of Classical Studies in Athens.