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This article contains major plot details or explains info that the player may want to find out on their own.
The MPO Mars Station is an underground Mars colony and is the setting for Subterrain. It is split into seventeen sectors, only two of which (the MPO Prison and Central Control) are powered and accessible at the beginning of the game. Exploring these sectors is the major activity performed within the game. The sectors can be broadly split into three groups of four - core, inner, and outer - with the Prison, Central Control, Murray Space Center, and Murray Mansion forming a special set of their own.
The prison is where Albert West begins the game, and is the setting for the tutorial. After escaping his cell and picking up some basic equipment, West makes his way to Central Control to try to figure out what went wrong - and maybe find a way off the planet.
Central Control is the hub of MPO, containing living quarters, a suite of remote control stations for the station's various harvesting, processing, and production facilities, as well as the Nano Reconstruction Bay and the Power Generator.
The core sectors are those directly connected to Central Control by stairways, and are thus the only ones reachable without the use of the tram. They have the lowest power requirements at 1300 units each. There are four core sectors.
Nilson Engineering is the primary producer of most of the colony's supplies, and is where West can find the 3D Printing System, Bio Combine System, MPO Bio and Tech Recycle Systems, Bio Processing System, and Ore Refining System. The 3D Printing and Bio Combine Systems are used to produce items; an item can only be produced after the appropriate blueprints are obtained from researching in Herbert Research. The Bio and Tech Recycle Systems allow West to break down a variety of items into their core materials, and are the primary sources of some of the most important materials, such as electronic resin. The Bio Processing and Mine Ore Refining Systems can refine the produce from the Biosphere and Mine, creating materials that can be useful in producing some items.
Herbert Research contains the Bio Research System and Tech Research System. Both systems work similarly in that they solely research whatever items are given to them; the only difference between the two systems is the types of items that they can research. The Bio System works with items tagged with "Researchable Bio", and the Tech System works with "Researchable Tech". Similarly, any researched bio can be produced at Nilson Engineering's Bio Combine System, while researched tech can be produced at the 3D Printer.
The Biosphere contains the computer-controlled facilities necessary for growing plants on Mars, which West can process into useful resources via Nilson Engineering's Bio Processing System. The plants can also be eaten raw if necessary, but given the chance of contamination, it is not recommended.
The Mine contains a fully automated mining rig that can extract ore from the Martian crust. West can then process this ore into useful resources via Nilson Engineering's Ore Refining System.
The inner sectors are those closest to the core, requiring only a 20 to 30 minute tram ride to reach. They draw 1800 units of power each. Each inner sector has six floors (numbered 0 to 5; all but floor 0 are randomly generated), connected by stairs and (once West switches them on) powered elevators, and each of them hosts one of the four level 2 data chips on a random floor. They all have an oxygen generator on a random floor and a thermal generator on the last floor. All inner sectors are completely dark until the corresponding floor's power is switched back on.
It is important to note that all of these sectors are entirely randomized for every playthrough, except for the ground floors of each sector. The rooms with the data chips will retain the same structure, but may be rotated, may be found on any non-ground floor, and may be almost anywhere on the floor itself.
The location of the Plasma Launcher blueprint and level 2 Engineering Data Chip. The keycard needed to get inside the room with the blueprint is located in a bedroom in Herbert Research. The data chip room is a simple living suite, with the data chip in a suitcase.
The location of the level 2 Research Data Chip, found in a large, square room with a vent in each corner. The chip is found in the ventilation system, laying on the ground near a dead cat. On F05, a marsmari D can be found in a bag, near the only journal of the sector.
The outer sectors are further away from Central Control, requiring a tram ride lasting around an hour and a half to reach. They draw 3300 units of power each. Each outer sector has eleven floors (numbered 0 to 10; all but floor 0 are randomly generated), connected by stairs and (once West switches them on) powered elevators. All outer sectors are completely dark until the corresponding floor's power is switched back on.
Each sector hosts both one of the four level 3 Data Chips as well as one of the four Level 4 Data Chips. The floor and location of the chip in each sector is random, but level 3 chips are always between floors 1 and 5 and level 4 chips are always between floors 6 and 10. Each sector also has an oxygen generator on a random floor and a thermal generator on the last floor that supply the entire sector.
It is important to note that all of these sectors are entirely randomized for every playthrough, except for the ground floors of each sector. The rooms with the data chips will retain the same structure, but may be rotated, may be found on any non-ground floor, and may be almost anywhere on the floor itself.Level 3 Research Chip and the Level 4 Mining Chip. The level 3 research chip is found in a "Better Bar"; the room with it has about 60 Better Bars on the ground, but only one contains the chip (attempting to open the wrong bar will contaminate West). The correct bar's X is a brighter red and the lower-right portion is slightly shorter.
Location of the Level 3 Biosphere Chip and the Level 4 Research Chip. The level 3 chip requires Zeronica Jones' keycard. The level 4 chip is at the end of a circular hallway, inside the lone cat; the cat must be killed in order to get the chip.
The Space Center is the furthest sector from Central Control, requiring a 1 hour 45 minute tram ride to reach, and has by far the largest power draw of any individual sector, requiring 5000 units. Accessing the Space Center in an attempt to escape the Red Planet quickly becomes West's main objective. A Broken Navigation Module is found near Shuttle 2 and Space Suit Plans in the southwest corner, which must be researched in order to escape.
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Murray Mansion is not initially visible on the map, but is accessed after West attempts to escape. It holds the Purification Data that West needs in order to eliminate the mutants from the MPO colony. After this is done, he returns to the Mansion to face the final mutant.