Rhodes is a maritime crossroad between east and west. Due to that, always had fortresses and castles for its defence. Especially in times of Byzentine Empire but also during the Knights occupation. Here is a list of the most famous.

1. Palace of the Grand Master
The Palace of the Grand Master of the Knights of Rhodes, also known as the Kastello (Greek: Καστέλο, from Italian: Castello, “castle”), is a medieval castle in the city of Rhodes, on the island of Rhodes in Greece. It is one of the few examples of Gothic architecture in Greece. The site was previously a citadel of the Knights Hospitaller that functioned as a palace, headquarters, and fortress.

2. Archangelos Castle
“Archaggeloskastro” is located in Kerami at an altitude of 200 meters above sea level, 27 Km south of Rhodes Town and a short distance from the coast.
It is built on a rock 217 meters high, east of the Village of Archangelos and has an elliptic shape.
As mentioned in the decree Knights it was built in the 15th century to effectively protect the villagers from any danger. The earliest findings date back to 1100 BC. Today it is a restored monument.

3. Castle of Monolithos
It is located on the top of a huge solitary rock near the coast. Built in the 14th century by the Knights in order to have control of the sea and protect the inhabitants from pirate raids. Inside the castle you can find rescued cisterns and the ruins of the Church of Saint Panteleimon.
The view from the castle is breathtaking.

4. The Medieval Castle of Kritinia
It is Located 2 kilometers northwest of the Village Kritinia and 55 kilometers from the city of Rhodes.
It is a blend of Byzantine and Medieval style that is known as Kastelli. Inside are the remains of the Catholic Church of Saint Paul and newer buildings, as the castle was used during the Italian occupation as a sea base.

5. The Knights Castle of Asklepio
This is located on a hill 250 meters high in the Village Asklepio. Built in 15th century in 2 phases: the first fortified the square tower and the second tower in the northwest corner was repaired.
The castle was built to protect the settlement of the village, since its location allowed the supervision of a large section of coastline and inland roads. The perimeter wall is 1.30-1.50 meters thick.
Inside the fortress there are two cisterns and ruins.

6. The Feraklos Castle
Castle built near the village of Malona on a hill 85 metres high overlooking the sea between the bays of Ayia Agathe and Charaki. It is also known as Faraklo or Charaki. Its remains date from the Byzantine and Hospitaller periods. One gate and two 15th c. round towers still survive to the south and southeast. The arms of the Order of St. John and of grand master G. B. degli Orsini are incorporated in the masonry facing the sea. The conquest of Feraklos by the Knights Hospitaller on 20 September 1306 was the first success of the Order in its endeavout to conquer the island. Before 1408 the castle was deserted. It was repaired under grand masters Orsini (1467-1476) and Pierre d?Aubusson (1476-1503), for the protection of the fertile territory around and the nearby anchorages.