The fort Boyard or Vauban's moon
This squat building standing in the middle of the sea, was raised on an artificial island in the reign of Louis XIV in order to protect Rochefort harbour.
Vauban, sent by the king to raise it, said: "It would be easier to catch the moon with teeth than trying to do such a task in such a place!"
So the plan was abandoned... and picked up in the beginning of the 19th century: Napoleon, first Consul, launched the construction of a stronghold (80 metres long), began in 1804.
Then, troubles began! First, a terrible storm destroyed half of the stones. Then, in March 1809, an English frigate machine-gunned the workers, who took shelter in Boyardville, a city they had built on Oléron island, few months ago.
Enemies' fire-ships (boats full of inflammable materials) exploded in April 1809 near the stronghold. The building site stopped... and continued in 1842, thanks to admiral Rosamel. The whole thing ended in 1866!
The stronghold was transformed into a jail for Communards in 1871. The sea spray, the icy temperature, the lonely position in the middle of the sea... whoa, fort Boyard was a Hell in sea!
In 1872, prisoners were transferred in Saint-Martin-de-Ré. Well, you know, in the Second Empire, the stronghold was considered as a masterpiece! They even reproduced a small-scale model for the Universal Exhibition of 1867!