Looked up Murania on Google - - found this:
From the "League of Extraordinary Gentlemen" WIKI,
Murania is an advanced subterranean empire and outpost of the massive underground land Atvatabar, which is located 25,000’ beneath the U.S. state of New Mexico. Coincidentally a ranch was built above Murania, belonging to early 20th-century gunfighter and balladeer Gene Autry.
The inhabitants of this subterranean empire were descendants from the sunken continent of Mu that had become so used to their underground environment that they could no longer breath normal air, having to rely on oxygen masks to survive on the surface. The Muranian Empire is quite advanced, complete with towering buildings, robots, ray-guns, and elevator tubes that extend miles from the surface. The realm also contains a massive amount of radium deposits.
Murania is based from the film The Phantom Empire (1934), which starred Gene Autry as himself.