The Petite Ceinture — "little belt" — is an abandoned railway line that circles inner Paris, threading through tunnels, along embankments, and through cutting past the backs of buildings that have grown up around it. Built in 1852 to connect the main terminus stations without crossing the centre, it operated as a passenger line for 82 years before being replaced by the Métro. The trackbed was simply abandoned in 1934 and left to regenerate.
Several sections have been opened as linear parks and walking paths, particularly in the 15th, 16th, and 20th arrondissements. The stretch through Belleville and Ménilmontant in the 20th is particularly atmospheric — trees and shrubs have grown up between the rails, and the cutting walls carry decades of street art. Access points vary; the city is gradually converting more sections into publicly accessible promenades, and some sections remain technically off-limits but widely visited.