The old city is surrounded by walls, and the streets are arranged in a herringbone pattern allowing free circulation of air but protecting against strong winds. Korčula is tightly built on a promontory that guards the narrow sound between the island and the mainland. Building outside the walls was forbidden until the 18th century, and the wooden drawbridge was only replaced in 1863. All of Korčula's narrow streets are stepped with the notable exception of the street running alongside the southeastern wall. The street is called the Street of Thoughts as one did not have to worry about the steps.
The town's historic sites include the central Romanesque-GothicCathedral of St Mark (built from 1301 to 1806), the 15th-century Franciscan monastery with a beautiful Venetian Gothiccloister, the civic council chambers, the palace of the former Venetian governors, grand 15th- and 16th-century palaces of the local merchant nobles, and the massive city fortifications.
The devout Catholic inhabitants of Korčula keep alive old folk church ceremonies and a weapon dance, the Moreška, which dates back to the middle ages. Originally danced only on special occasions, in modern times there are performances twice a week for tourists.
The city's Town Statute  dating back to 1214 prohibited slavery, making Korčula the first place in the world to outlaw the practice.
Korčula, like other islands and many coastal cities in Dalmatia, displays a dual Latin-Slav culture which developed from the late Roman era to the emergence of the modern Croatian state. Until the late 19th century, people identifying as Italians formed part of the population of Korčula town while the rest of the island was almost completely inhabited by people identifying as Croatians. However, historically the distinction was often ambiguous and local identity (eg di Curzola, Dalmata) usually took precedence over these fixed categories. The island therefore possesses a distinct Mediterranean cultural personality which sets it apart from the mountainous hinterland and continental Croatia further north. The town is revered for being the possible birth town of the famous Venetian merchant, Marco Polo, who was born around 1254. This is based on written evidence that Marco's family originated in Dalmatia and then settled in Venice, and that the Depolo surname, which has existed in Korčula at least from the 13th century, is linked to his family.