This is a former city boundry. There used to be trenches with city walls. But the trenches is nowadays all that is left over. In 1830 the trenches were thought necessary as a second water output from the lake. The left over wall from baroque times was taken away. During instustrialisation factories were settled along the Schanzengraben. It was used as factory canal. Later it was thought that a recreation area for pedestrians should be created. The reconstruction started in 1975 and ended in 1984.
You can walk from Gessner brigde near the main railway station all the way to the lake or vice versa. It is very pleasant, people often sit there with their home made or take away lunches.
During rain or in winter part of the foot path can disappear under water or the wooden planks can get very slippery.
Want to take a nice walk and see Zurich from a different angle? Walk along the small river called Schanzengraben that starts by the lake and ends by the main station.
Built to protect one side of Zurich in medieval times, it's now a nice place to walk, especially in the summer.
Beware: After heavy rains, the path can be flooded.