A 'String' Theory for High Speed Rail
"The UST uses steel or concrete rails, reinforced by hundreds of high-tension wires running through the middle of the rail, suspended above the ground on towers approximately 30 m apart. Unlike roads or rail systems, it can traverse mountains and other rough terrain in a straight line, and it's equally adept at crossing shallow waters, desert or forest, with minimal environmental impact at the ground level."
The post goes into much detail about the idea, including a series of videos and renderings of what such a system could look like. The idea has been in the works since the 1970s, but there have been no built prototypes.