Ghost Stations of the Paris Metro
I find it facinating that in a growing population that large places like Paris have stations that became disused.  But that seems to be the case upon many large underground networks that have been around long enough and in London the list is not short: <a href="https://tfl.gov.uk/corporate/about-tfl/culture-and-heritage/londons-transport-a-history/london-underground/disused-underground-stations" rel="nofollow">https://tfl.gov.uk/corporate/about-tfl/culture-and-heritage/...</a><p>Though that does not include stations part built and then never completed of which there are a fair few for London, unsure about Paris but I would imagine be some instances of part built or intended stations that never got finished.
Indeed I had a look at seems at least two got built and never saw use - <a href="https://www.renfe-sncf.com/rw-en/blog/destinations/paris/visit-underground-stations" rel="nofollow">https://www.renfe-sncf.com/rw-en/blog/destinations/paris/vis...</a>