Palace of the Grand Master of the Knights of Rhodes

Recent study places the foundations of the ancient temple of the sun god Helios on the ground beneath the palace, and makes the same spot the probable site of the Colossus of Rhodes. The building itself began in the late 7th century as a Byzantine citadel. When the Knights Hospitaller occupied Rhodes in 1309, they converted the fortress into their administrative centre and the palace of their Grand Master, repairing it and making major modifications in the first quarter of the 14th century. The earthquake of 1481 damaged it, and it was repaired soon afterwards.

The Ottomans captured the island in 1522, and the palace served thereafter as a command centre and fortress. In 1856 a gunpowder magazine beneath the nearby Church of Saint John — possibly stored there since the siege of 1522 — was struck by lightning. The explosion killed many people, destroyed the church and brought down most of the palace's upper floors; only the ground-floor rooms survived.

Under Italian rule the Ottoman-era structures of the former palace were demolished, and the authorities under Cesare Maria De Vecchi, governor of the Dodecanese, asked the architect Vittorio Mesturino to design the reconstruction of the palace and of the nearby Street of the Knights. With no remains or documentation of the pre-Ottoman building to work from, he produced a structure that suited the authorities' need for a functional government building carrying the aura of the Hospitaller legacy. The work was carried out between 1937 and 1940.

It has been criticised since for its lack of historical accuracy and for unnecessary alterations to the castle's authentic remains, one scholar calling it "horrendous fascist taste". The rebuilt castle became a holiday residence for Victor Emmanuel III, King of Italy, and later for Mussolini, whose name can still be seen on a large plaque near the entrance.

The peace treaty signed with Italy on 10 February 1947 determined that the new Italian Republic would transfer the Dodecanese to Greece, and Rhodes passed over in 1948. The palace became a museum, and in 1988, during the Greek presidency of the European Economic Community, Andreas Papandreou and the other EEC leaders held a meeting in it.