The river Ill has for a long time been a threat as well as an economic advantage for Strasbourg. Beside the natural hazard, enemies could actually use it to sneak inside the defensive perimeter and especially between the layers of the defence, as the river served as a separation between the inner walls and the outer fortifications. The upstream part was especially vulnerable, because it was also one of the side an attacker would the most probably chosen to besiege the city.
This part of the fortification have consequently been subject to special care since the Middle-Ages. In 13th century, a fortified bridge was constructed and regularly reinforced throughout ages (you can see it here). But at the end of the 17th century, this fortification was considered outdated and the authorities decided thus to build in 1685 a second line a bit upstream.
The famous French military architect Vauban draw the new structure, which was constructed between two existing bastions constructed around 1670. It was this time not only a fortified bridge, but also a dam: in case of an attack, the arch were blocked, consequently flooding all the South-West surroundings of the city. The system was used only once, during the siege of 1870, interfering only slightly with the attack: at that time, canons had a way longer range than in Vauban’s era and it consequently didn’t prevent to Prussians to install artillery on the West side of the city, allowing them to obtain the surrender after a deadly bombing (more than 6000 shell each day during 42 days).
To avoid an enemy to cross the river in case he took one side of the bridge/dam, it is inside divided in independent parts separated by drawbridges.
Originally, the building was covered with a half-timbered structure and a saddle roof, but those were replaced by a masonry covered with an embankment of earth to improve the resistance to modern artillery. The top has been converted in a terrace for tourists in 1966 and the whole dam has been restored between 2010 and 2012.
Tools and exifs:
- Canon EOS 450D + Canon 18-55mm IS
- 30 s.
- ISO 100