Bordeaux Transporter Bridge (unfinished)
The pont transbordeur de Bordeaux was intended to cross the River Garonne.
It was designed by Ferdinand Arnodin, and featured an unusual suspension system.
Construction began in September 1910.
If it had been completed, with its 400 m (1312 ft) span, it would have been the longest transporter bridge in the world. The longest transporter bridge which was actually completed was the Widnes and Runcorn Transporter Bridge, with a span of 305 m (1000 ft). The longest example built to the design of Ferdinand Arnodin was the Newport Transporter Bridge, with a span of 197 m.
The work was interrupted by the war in 1914, when the construction of the two 95 m high pylons was completed.
No progress was made, and in 1938 it was formally agreed to abandon the project.
The pylons were destroyed by the German authorities in August 1942. Only the masonry piers of the pylon on the right bank of the Garonne and the corresponding anchor blocks have survived.
The above information was largely condensed from the Wikipedia entry.
More information, with numerous illustrations here.