The Corinth Canal is out of this world
This is an artificial canal in Greece that connects the Ionian Sea’s Gulf of Corinth with the Aegean Sea’s Saronic Gulf. It cuts through the narrow Corinthian Isthmus and separates the Peloponnese from the Greek mainland, effectively making the peninsula an island. Unfortunately, the canal was closed after a landslide.
The canal was dug at sea level through the Isthmus and has no locks. It is impressively 6.4 kilometers (4 miles) long and only 21.4 meters (70 feet) wide at its base, making it inaccessible to many modern ships. It is now primarily a tourist attraction since it has little economic significance.