Quite by oversight, we ended up changing Métro trains at Montparnasse station. We were en route from the Eiffel tower to the 5th arrondissement when habit took over and our guide put us on the train to her place, rather than our intended destination. As it turns out, her absentmindedness was a gift in disguise, for the Montparnasse station, unlike anywhere else in the world, has high speed moving walkways!
C. lit up as soon as he saw them. Eight months or a year or so ago, we'd read an article on the installation of high speed moving walkways. (Perhaps it was this one?) For the first few weeks, staff was required to warn users to be careful, to train them in how to use the device. While most of it is just like any other moving walkway, the beginning and ends are not. A few yards of fine-grade rollers bring pedestrians up to speed. The trick - as lots of signs and animated warnings indicated - is to not walk on the rollers, to keep ones' feet flat and still until up to speed. Likewise on the rollers at the end, which bring pedestrians back down to normal speed.
In the long stretch of middle, the walkway runs at a lovely 9 kilometers per hour. (Most run at 3 km/h.) The Wikipedia tells me that when the walkway first opened, it ran at 12 km/h, but too many people fell over, unbalanced by the shift in speed.
All three of us came off of the walkway elated by the experience. It was just so neat.