Project Cerberus was centered around development of the mat-trans system, or teleportation. They started with two small metal spheres over a few inches, gradually increasing and expanding over time until they could make a huge chamber that could transport living beings thousands of miles. See the section on gateways for more details on how the process works.
In Greek mythology, Cerberus, often referred to as the hound of Hades, is a multi-headed dog that guards the gates of the Underworld to prevent the dead from leaving. He was the offspring of the monsters Echidna and Typhon, and was usually described as having three heads, a serpent for a tail, and snakes protruding from multiple parts of his body. Cerberus is primarily known for his capture by Heracles, one of Heracles' twelve labours.