The Rue de l’Avenir, or Street of the Future, was an electric moving walkway that was installed at the 1900 Exposition Universelle in Paris. This innovative attraction ran along the edge of the Exposition site and consisted of a fixed platform and two mobile platforms on a viaduct. Passengers could board at one of the nine stations along the route. The sidewalk moved at speeds of 4.2 km/h and 8.5 km/h, making it possible to complete the loop in just 26 minutes. The sidewalk could accommodate up to 14,000 people at a time and was a popular attraction at the Exposition.
https://en.wikipedia.org/wiki/Rue_de_l%27Avenir