Island Of Poveglia, Venice, Lido, Venetian Lagoon, Italy

In the 20th century the island was again used as a quarantine station, but in 1922, the existing buildings were converted into an hospital for mentally ill and long-term care. This went on until 1968, when the hospital was closed, and the island, after being shortly used for agriculture, was completely abandoned. Presently, the island is closed to locals and tourists and remains under Italian government.
Use by Napoleon
Poveglia island was used by Napoleon Bonaparte much to store weapons during the Napoleonic Wars. He used this location for the reason that it was small and insignificant to the Austrian Empire. Contrary to his belief, there were many small battles on this island as somehow the information of his weapons being there leaked to Austria.