There are hundreds of large cities miles beneath the earth, many of which are interconnected by tunnels through which high speed shuttles navigate, using magnetics for propulsion.

Some of these are government or scientific installations while others are more alien or otherworldly bases. Some of these cities or communities are located in or under mountains while others are in large underground caverns. Nearly everyone knows about Telos a mile or so beneath Mt. Shasta in California.

Not everyone knows that nearly every major city on the planet has its roots in an inner city beneath it. Secret elevators or shafts in some buildings lead to these duplicate cities, to which only certain individuals are allowed or have access to. Most underground cities are built for protection in times of war or natural catastrophes, as well as for secret and often forbidden projects or activities.