The city was destroyed by an earthquake in 375 and again in 551. During Alaric's invasion of Greece, in 395–396, Corinth was one of the cities he despoiled, selling many of its citizens into slavery.
During the reign of Byzantine emperor Justinian I, a large stone wall was erected from the Saronic to the Corinthian gulf, protecting the city and the Peloponnesean peninsula from the barbarian invasions of the north. The stone wall was about six miles (10 km) long and was named Examilion (exi=six in Greek). During this era Corinth was the seat of the Thema of Hellas (representing modern day Greece).
In the 12th century (during the reign of the Comnenus dynasty), the wealth of the city, generated from the silk trade to the Latin states of western Europe, attracted the attention of the Sicilian Normans under Roger of Sicily, who plundered it in 1147.