Ada Kaleh (Turkish for "Island Fortress") was a small island on the Danube populated by Turks that was submerged during the building of the Iron Gates hydro plant in 1970. The island was about 3 km downstream from Orşova and measured 1.75 by 0.4-0.5 km.
The isle of Ada Kaleh is probably the most evocative victim of the Đerdap dam's construction. A Turkish enclave, it had a mosque and a thousand twisting alleys, and was known as a free port and smuggler's nest. Many other ethnic groups lived here beside Turks.
It was walled: the Austrians built a fort there in 1669 to defend it from the Turks, and that fort would remain a bone of contention for the two empires. In 1699 the island came under Turkish control, from 1716 to 1718 it was Austrian, after a four month siege in 1738 it was Turkish again, followed by the Austrians re-conquering it in 1789, only to have to yield it to the Turks in the trailing peace treaty. Thereafter, the island lost its military importance.
In 1804, during the First Serbian Uprising Serbian rebels, led by Milenko Stojković, caught and executed the dahias, who had fled from Belgrade and took refuge on the island. It was the oppression brought by the dahias that was the direct cause for the uprising.
The 1878 Congress of Berlin forced the Ottoman Empire to retreat far into the south, and the island came under the control of Austria-Hungary, though it remained the property of the Turkish sultan. The inhabitants enjoyed exemption from taxes and customs and were not conscripted. In 1923, when the Ottoman monarchy had disappeared, the inhabitants chose to join Romania.
The population lived primarily on the cultivation of tobacco and fishery, later on tourism. In its last years of existence the island counted 600 to 1,000 inhabitants.
With the building of the dam, some of the structures built on the islands were moved to nearby Şimian Island, including part of the masonry of the fortress' catacombs, the Mosque, the bazaar, Mahmut Pasha's house, the graveyard and various objects. However, the Ada Kaleh community decided to emigrate to Turkey after the evacuation of the island instead of re-settling on Şimian island. Also, a smaller part went to Dobruja, another Romanian territory with a Turkish minority.
Ada Kaleh plays an important part in the novel of one of the most famous Hungarian authors, Mór Jókai. In the novel "The Golden Man" (Arany ember), published in 1872, Ada Kaleh is called the "Island of Nobody" and it becomes an almost mythical symbol of peace, seclusion and beauty, juxtaposed with the material outside world.