Title: Paris : des hauts et des bas, Paris de Haut
PDF of the article by Gilles Thomas:
"Under Paris exists another Paris,
or more precisely an image of what
Paris looked like more than 200 years ago. We used to name it “the
topographic blueprint of the XVIIIth century in Paris”. It’s the city
with its streets, crossings, stairs, streetnames, monuments’ names and
ground level indications.
Below Paris you still walk in Paris!"