They were built by the Knights Hospitaller of Saint John by enhancing the existing Byzantine walls starting from 1309, the year in which they took possession of the island after a three-year struggle.

[1][2] Like most of the defensive walls, they were built with a technique[3] called rubble masonry which allows for a great mass capable of withstanding gunshots with smooth external stone faces to prevent climbing.

Philo of Byzantium author of the treatise "Paraskeuastica" on defensive works, stayed in Rhodes in the 3rd century BC and expressed his admiration for its walls.

The expansion of the walls was undertaken by Grand Master Antonio Fluvian de Riviere who allowed the (medieval) town of Rhodes to reach the current area of about 42 hectares (104 acres).

The Byzantine fortifications were demolished leaving just a portion of those of the old fort known at the time of Knights as Collachium (Greek: Κολλάκιον).

A new Ottoman siege could not be withstood, so the Knights made available their great financial resources and in a very short time the most important palaces of the town and the fortifications were rebuilt.

In the following years Grand Masters Pierre d'Aubusson, Emery d'Amboise, Fabrizio del Carretto and Philippe Villiers de l’Isle Adam ordered the fortifications to be rebuilt to withstand the cannons.

Among them Matteo Gioeni, Basilio della Scuola, Gerolamo Bartolucci and Gabriele Tadino da Martinengo.

The Gate of St John (Πύλη Αγίου Ιωάννου) is commonly known as Koshkinou or Porta Kokkini (Πόρτα Κόκκινη, "red door").

Its defensive towers have a representative task more than defence in facts due to the reduced space between the waterfront and the walls no army could have ever attempted an attack from this side of the fortifications.

Today thanks to the direct connection with the Liberty gate it allows a fast flow of vehicles between the Kolona harbour and the new town.

The Gate (in Greek: Πύλη Αγίου Παύλου) was built in the second half of the 15th century to allow the access to the fortified city and the Kolona harbour.

It has a pentagonal shape and represents one of the examples of a gate transformed into a bastion through subsequent modifications that took place until the final siege of 1522.

With the addition of the powerful terreplein of Spain the Bastion of Saint Georges is the model of the successive modern forts.

It final transformation was designed by the Italian architect Basilio della Scuola and carries coat of arms of the latest Grand master in Rhodes Philippe Villiers de l’Isle Adam.

Grand Master Fabrizio del Carretto had it armoured with a chemin de ronde to hold cannon emplacements.

It was built between 1396 and 1421 by the Grand Master Philibert de Naillac before the development of the cannons on the mole east of the Gate of Saint Paul that closes the commercial harbour.

It was built on the natural mole East of the harbour by the Grand Master d'Aubusson who had the coat of arms of France placed on the tower (hence one of its names).

The Mandraki (in Greek Μανδράκι) was the military harbour and was guarded by a tower built between 1464 and 1467 by the Grand Master Zacosta at the end of the natural mole.

After the siege of Rhodes in 1480 the Grand Master d'Aubusson added a bastion around the tower transforming it into a guard fortress on the sea.

All the built-up elements dating before 1912 have become vulnerable because of the evolution in living conditions and they must be protected as much as the great religious, civil and military monuments, the churches, monasteries, mosques, baths, palaces, forts, gates and ramparts.