A few weeks ago I passed a double-decker bike chained to a light post on rue Cabanis. I stopped, ogled, then took a few pictures. After doing some internet exploring* this evening, I’m pretty sure the bike above is TallTwin. You can see TallTwin in action here.
*I started by looking for double-decker bikes but quickly learned that I was looking for a Tall Bike, not to be confused with an Upside-down bike. An early version, perhaps the mother of the Tall Bike, was called a Giraffe bike (un velo giraffe), also known as the Eiffel Tower Bicycle. The Eiffel Tower (Giraffe) Bicycle was designed by Parisian Leon Lyon and built in Beeston, Nottingham, England. You can read an article from the April 4. 1895 Toledo Blade titled: Eiffel Tower Bicycle here.
This site has great pictures of very old tall bikes like the 1896 Nelson Special and a 1915 ‘bunk bed’ vertical tandem.