Two foot and 600 mm gauge railways are narrow gauge railways with track gauges of 2 ft and 600 mm, respectively. Railways with similar, less common track gauges, such as 1 ft 11+3⁄4 in and 1 ft 11+1⁄2 in, are grouped with 2 ft and 600 mm gauge railways.

The Maginot Line, named after the French Minister of War André Maginot, is a line of concrete fortifications, obstacles and weapon installations built by France in the 1930s to deter invasion by Nazi Germany and force them to move around the fortifications. It was impervious to most forms of attack; consequently, the Germans invaded through the Low Countries in 1940, passing it to the north. The line, which was supposed to be fully extended further towards the west to avoid such an occurrence, was finally scaled back in response to demands from Belgium. Indeed, Belgium feared it would be sacrificed in the event of another German invasion. The line has since become a metaphor for expensive efforts that offer a false sense of security.