St Catherine's Gate (or Sea Gate) was the main gate of the town. It was built in 1478 by Grand Master Pierre d'Aubusson as part of an effort to strengthen the fortifications of Rhodes against a much feared Ottoman attack: the attack actually occurred just two years later.
The gate however was unlikely to be the site of a possible assault by the Ottomans: the space between the walls and the harbour was too limited to allow the enemy to establish his camp there. This explains why the gate is more a work of art, a sort of grand entrance, than a defensive structure. The relief portrayed the Virgin Mary between (left) St John and (right) St Peter. The coats of arms below the relief showed the heraldic symbols of the King of France (centre), in addition to those of the Order (left) and of the Grand Master (right).
The old town is encircled by strong medieval walls, a typical example of the techniques of fortification of the 14th-15th century built by the Knights of Saint John to protect the city from all dangers. The impressive walls (with a total length of 4 km) with their wide ramparts are reinforced at intervals towers, while the entrance to the medieval town is through eleven magnificent gates.