The Destruction Beam is a delicate piece of tunneling technology used by Laserbeak. Its beam can slowly chew through bedrock to create artificial earthquake faults, which can then be exploited by the Decepticon Rumble.
Chance discovery by the Autobots derails these plans.
The Decepticon fortress is located in the hills outside Center City. A number of concealed entrances allow entrance to the fortress, but they are booby-trapped to anyone passing through them without the proper codes.
Megatron has a concealed room deep in the fortress, poshly laid out and carpeted (!), from which he may observe all that takes place within, watching his own troops for any sign of disloyalty.
A series of natural cave systems form an unintended 'back entrance' to the fortress, leading into the storage rooms.