Decauville was a manufacturing company which was founded by Paul Decauville, a French pioneer in industrial railways. Decauville's major innovation was the use of ready-made sections of light, narrow gauge track fastened to steel sleepers; this track was portable and could be disassembled and transported very easily.
The first Decauville railway used 400 mm gauge; Decauville later refined his invention and switched to 500 mm and 600 mm gauge.
Wikipedia https://en.wikipedia.org/wiki/Decauville
Address 26 Avenue de Navagne, Visé 4600, Belgium
Coordinates 50°44'27.989" N 5°41'38.785" E