The most recognizable landmark that define the physiognomy of the historical city of Dubrovnik and give the city its characteristic and world known reputation are the untouched city walls; the walls surround the city with a total length of 1940 metres. This complex fortress, one of the most beautiful and solid fortress systems on the Mediterranean, is composed of a range of forts, bastions, casemates, towers and freestanding fortresses. The walls were constructed during difficult times when the city and Republic were in constant danger; the walls have been maintained today not only because of the knowledge of the skilled construction workers and the constant care provided by city dwellers that maintained and rebuilt the structures as needed, but because of the brilliantly reputed diplomacy in Dubrovnik which managed on many occasions to avoid dangerous measures taken by enemies against the Dubrovnik Republic.
The Dubrovnik Old Town is completely surrounded by walls and fortresses, including the Old City Port. The history of the fortifications in Dubrovnik goes back to the early Middle Ages. It is certain that the early town on Laus Island was also surrounded by defensive walls. The fact that Dubrovnik managed to survive the fifteen month long invasion by the Saracens in the 9th century proves how well the city was fortified. The city first spread towards the uninhabited eastern part of the island. That is why the current name for the southeast part of the city, next to the Fort of St. John, Pustijerna, comes from the Latin statement "post terra", which means outside the town. In the 9th and 10th century, the defensive wall enclosed the eastern portion of the city. In the 11th century, when the narrow sea strait where Placa is located today dried up, the city was connected to the village that already existed on the coast; and soon afterward, a single defensive wall was constructed around the area which today is equal to the size of the core of the Old Town. In the 13th century, the entire city was surrounded by the defensive walls except the Dominican monastery, which entered into the city defensive walls in the 14th century. On average, the walls were 1.5 metres thick, constructed of stone and limestone. In order to strength the wall surfaces and improve defence, 15 square towers were constructed in the 14th century. Large works were completed at the end of the 14th century after the city was finally liberated from Venetian rule. The largest stimulus for continued development and emergency repairs and works of the Dubrovnik fortresses came with the unexpected danger of attack by Turkish military forces after they took over Istanbul in 1453; the city was also under danger latent danger of attack by the Venetians. Due to a great efforts by the citizens and rulers of Dubrovnik, as well as the talents of many skilled workers who were brought in during the emergency, most of the land facing parts of the fortress were strengthened; all this, along with the construction of fortresses and the semi-circle bastion on the bulwark, was completed in less than three years. The system was expanded and modernized during the 16th century, and later. Today's extent of the city walls dates back to the 16th century, while the definite appearance of this system dates back to what we call the Golden Age of Dubrovnik, from the fall of Istanbul in 1453 to the catastrophic earthquake that devastated Dubrovnik in 1667. The main walls on the landside are between 4 and 6 metres thick, while the walls on the seaside range from 1.5 metres to 3 metres in thickness. At certain locations, the walls reach up to 25 metres in height. On the landside, the wall is protected with an additional range of slanted supporting walls, to provide defence from cannons. The irregular parallelogram, which surrounds Dubrovnik, has four strong fortresses at its most significant points. To the north is the strong circular tower Fort Minceta, to the east side of the city port is the Revelin Fortress, and the large and complex Fort of St. John is located on the southeast side of the city. The western entrance to the city is protected by the strong and nicely shaped Bokar Fort. The western side of the city is protected from land and sea attacks by the strong, freestanding Fort of St. Lawrence (Lovrijenac). Along with this outstanding fortification, the city walls are also protected by two additional round towers, 12 square towers, 5 bastions and 2 cornerstone forts, while the expanded bulwarks are flanked with one large and 9 small semi-circular bastions. Along the landside of the city fortification, a deep moat was added for extra protection. The entire fortification system also consisted of numerous cannons. The cannons were manufactured in local workshops, which Dubrovnik was recognized for in this part of the world. The most recognized cannon manufacturer in the 16th century was Ivan Rabljanin from Dubrovnik. In periods of full combat readiness, the Dubrovnik city walls were protected with over 120 cannons. Communication with the outside world was maintained with the city through two well-protected city gates, one placed on the western side of the city and the other placed on the eastern side. On the western side was the entrance to the city, the Pila Gates, which was complex and well fortified, while the eastern entrance, the Ploce Gates, was protected by the freestanding Revelin fortress. Both entrances and the city were constructed so that communications with the city could not be carried out directly; the messenger had to enter through multiple doors and walk down the winding passageway, which is evidence of the security measures taken as a last defence against the possibility of a surprise breach or entrance by unexpected visitors. In the city port area, one of the most significant areas of the maritime trade city, there were two entrances: Ponte Gate (port) and the Fish Market Gate.
The city port was protected from strong waves and surprise invasion by the Kase jetty. The entire layout of the Dubrovnik streets, as well as a range of expansions, was intended for fast and effective communication with the forts of the city walls. Today, a walk along the city walls is a true tourist attraction. From this viewpoint, it is easiest to understand the old city of Dubrovnik, as a different angle of the city opens from each new viewing point, especially when you look down upon the streets and squares which uncover an entire range of picturesque details. Here one can experience the atmosphere of the city and its layout in size and width, which is impossible to notice while walking along the city streets. Along with unforgettable images of the city, such a walk will reveal a magnificent view of the open sea before Dubrovnik and provides a view of the city surroundings.