A closer look

Nothing screams Parisian chic quite like ignoring the Eiffel Tower to trespass in a 19th-century railway trench. The Petite Ceinture, or 'Little Belt,' was a circular railway built around Paris in 1852 to connect the major terminals. Abandoned in 1934, the subterranean tunnels and sunken tracks have since transformed into an unauthorized urban wilderness, proving that nature aggressively reclaims the industrial revolution's footprint the moment humans stop paying attention.