1. Champ de Mars

Image via Wikimedia Commons

According to Pridian.net, this station on Line 8 near the Eiffel Tower has been converted into an extraction vent. For those familiar with the Paris metro, it’s located right between the stops La Motte-Picquet – Grenelle and École Militaire. The author at Pridian.net also points out the existence of toilets (squat-style) in the original Paris metro system, most which have been converted into functional closets, signal rooms and the like.