Square et Promenade Richard Lenoir

The ground beneath your feet hides one of the most significant engineering secrets in Paris. The boulevard was constructed directly over a long, vaulted tunnel that carries the Canal Saint-Martin underground. Baron Haussmann ordered this section of the canal buried between 1860 and 1862, essentially turning a bustling surface waterway into a hidden subterranean river. This massive project allowed the city to create this wide, tree-lined thoroughfare to improve traffic flow and military access in a district previously known for its narrow, difficult streets.