Extending deep into the Rocky Mountains is the former U.S. defense base, which houses a vast array of weapons that are refurbished and put to good use by the human rebellion.

Jonnie's first encounter with the defense base is much earlier than his first meeting with the Psychlos. When he was twelve he had strayed up there, more trying out a pony than going someplace. 

After riding for miles and miles he had been abruptly halted by giant, vertical doors, which he managed to pry open.