The Poterne des Peupliers is one of Paris’s psychogeographical hotspots. Historically at once both a barrier and a passageway, this portal into the city was a place that saw traffic stop, water flow and trains pass overhead. The legacy is not clearly visible, but the creations of a collective of street artists today highlight its significance.On one bridge is a railway line that is no longer used. Underneath, a road sits on top of the Bièvre river which has now been covered over. People are free to enter and leave the city as they please, with only traffic lights providing a brief pause to their progress. It would appear to be just an ordinary entrance point into the city today if it wasn’t for the creations on the walls of the various bridges.
If you arrive at this point via the tramway on the Boulevard Kellermann you will be following the city's 19th century Thiers fortifications. Some of the walls at the Poterne des Peupliers were originally part of those inefficient barriers, and it is on these walls that you can find creations by the inevitable Jerome Mesnager and Mosko et Associés, as well as more modern creations from Janaundjs. 
If the creations are here though it is not to mark the old city fortifications, but rather to plot the entrance into the city of the Bievre river. This hidden waterway is celebrated by a collective of artists known as the Lezarts de la Bievre who work together at various points along the ancient routes of the river across the city's left bank. The river is in the city's sewer pipes today, but this still seems like a highly significant part of the city. The picture below shows how it looked around 150 years ago (railway, river - more of a small stream in reality - passageway, and the peuplier (poplar) trees!), and although much of the surroundings have changed, the lines and axis remain the same. The city no longer has its physical barriers, but this is still a spot where energy flows in and out.










