The Forbidden Zone dome, known as the X-42 robo-warfare facility before the exile of Mobius, is a location in the northeast section of Big MT in 2281. It was originally named the X-42 robo-warfare facility but was changed by Mobius after he left the Think Tank. The door to this facility is locked until the player character has spoken to Doctor Klein as part of the main quest line Old World Blues.
The workshop area is comprised of a single, vast room that appears to occupy most of the inner volume of the building's dome. In the center is a large cargo elevator, on which resides the X-42 giant robo-scorpion. Around the perimeter of the room are several staircases leading to raised walkways and observation rooms, some containing terminals with information on the giant robo-scorpion. This information can be used to damage or disable the scorpion. One terminal, in particular, located on the highest catwalks in the room, indicates that it can be used to shut down the giant robo-scorpion remotely, but actually resets the giant robo-scorpion to no longer be hostile. Methods of assisting in attacking the giant robo-scorpion include activating turrets to fire upon it from a terminal and starting up target drones to keep it occupied in the same way.
The Forbidden Zone's dome is similar to The Think Tank's, but is in significantly worse condition: the lighting is a sickly green, the equipment is rusted, broken, or otherwise mostly unusable, and Dr. Mobius has covered most of the surface in the main room, specifically the center, with intricate scrawls of notes and formulas. In the six smaller rooms located off the upper tier, stored office furniture containing random loot can be found, along with what appears to be Dr. Mobius' private stash of Mentats. Located at the top of the main staircase, in a storage tank, is the Courier's brain. Unlike the Think Tank's dome, however, instead of five lights located on the front platform, there is only one.
- Audio Sample - Mobius' Robo-scorpion - On the center desk right in front of the north exit on the second floor.
- The emergency shutdown terminal password - By the Protectron containers in the northeast corner of the ground floor, near the last container.
- A LAER - In the northeast area of the building, to the right of the exit.
- Dr. Mobius' glove - On a table left next to the central stairs.
- Dr. Mobius' scrubs - In a trunk directly next to the central stairs.
- 44 Mentats - In the second farthest right room.
- A LAER - In the room left next to the central stairs.