There is a vast tunnel system throughout the United States for various reasons.
However, these tunnels were not built by the Masons but by the Army Corps of Engineers.
There are underground bunkers, of course, from where THEY would operate during a crisis and Central Command has underground factilities for the same reason.
There is an underground facility called Mount Weather that is self-contained and a virtual city.
Underground Bases Tunnels - Crystalinks
The many underground tunnels connect to one another. They are a network.
They connect to miitary installations and are used not only to bring their victims of "mind control" and victims of their pedophile rings to military bases for programming and NASA included, but to Bohemia Grove, as well.