Barrage Vauban

The Barrage Vauban, or Vauban Dam, is a bridge, weir and defensive work erected in the 17th century on the River Ill in the city of Strasbourg in France. At that time, it was known as the Great Lock, although it does not function as a navigation lock in the modern sense of the word. Today it serves to display sculptures and has a viewing terrace on its roof, with views of the earlier Ponts Couverts bridges and Petite France quarter.

Source: Wikipedia