Herodotus noted that the fortress was first built in 334 BC, by the Ionians. After Alexander conquered the fortress, he had it repaired due to its strategic importance. The passing years and various events wore down the fortress, and it was repaired together with the harbour, first during the time of Ibrahim Bey of the Mentese, then by Ghazi Ahmet Bey, sovereign of Marmaris. Sultan Suleiman the Magnificent, who used Marmaris as his base in the conquest of Rhodes in 1522 found the fortress too small and ordered a larger one to be built. In 1914 French warships bombed the fortress, causing great damage. This historic fortress made it to the present in a rather decrepit state, but was recently restored by the Ministry of Culture and Tourism Antiquities and Museums Directorate between 1980 and 1990.
The Marmaris Museum opened its doors to the public in 1991, and is located within the fortress at the city centre. The architectural structure of the fortress is very conducive to being a museum. The archaeological artefacts exhibited in the two covered halls and the garden, have been gathered from the vicinity. Amphorae, earthenware oil lamps, glass artefacts, weapons, arrowheads, coins, and ornaments from the Hellenistic, Roman, and Byzantine eras are among the exhibited items.
In the Ethnography Hall, displays include furniture, carpets, kilims, pots, and various items of kitchenware from the later Ottoman period.
The other covered halls are used as an art gallery, offices, and storerooms.