Alien Ruins
The Alien Ruins are vast, underwater caves that the player can encounter in Barotrauma. They are most commonly found embedded into rocks and ice found underwater.
Description
Alien Ruins are made up of long corridors and vast rooms of incredibly thick blocks. These rooms are particularly massive, possibly implying that their creators were larger than humans, with similarly large doors. Notably, these doors cannot be opened by conventional wiring, so attempting to make a submarine out of alien parts (as seen in the gallery) is all but futile. These ruins are often inhabited by a sole Fractal Guardian which can be a notable threat to an unprepared player. As always, a Diving Suit is required and a small Shuttle is recommended to get into an entrance of a ruin.
Obstacles
Rooms in the ruins sometimes contain traps.
Motion Activated Turret
This trap features a motion sensor activated turret that periodically switches on and off. It is powered by an Alien Power Generator, and can be disabled by removing the Alien Power Cell within.
Three Buttons
This obstacle features a door locked by a simple puzzle. It has 3 buttons, each of which toggle one or more of 3 lights. When all 3 lights are lit, the door opens.
Timed Button
This door has 2 lights beside it. One of the lights periodically turns on and off. When the button is pressed while the light is turned on, the second light lights and the door opens.
Roomful of Mooks
This room will have several monsters in it. Possible monsters include: Fractal Guardians, Crawlers, Husks
Loot
As well as the following Artifacts, the Alien Ruins can very rarely contain an 
Ancient Weapon, the strongest handheld weapon in the game.
Artifacts
Main article: Artifacts
Artifacts is the term given to a series of relics left behind by extraterrestrials on Europa. They are frequent targets of salvage missions in Quest Mode, and are potential sources of rare raw materials. Both the origin of these artifacts and their purpose is unknown.
Each artifact tends to have dangerous effects on their environment; for lack of understanding, they are impossible to prevent and can only be worked around. It is unknown how much of it comes from their intended function, normal side-effect of their working, or degradation sustained due to a lack of upkeep.
Five sorts of artifacts have currently been recovered from Europa, distinct in appearance, composition and effect: Psychosis, Faraday, Skyholder, Nasonov and Thermal.
Other
Amongst the alien ruins, the player can find various other items inside Small Alien Chests and Large Alien Chests.
Alien Power Cell
The 
Alien Power Cell is used to power Alien Weapons.
Alien Pistol
The 
Alien Pistol is a ranged weapon that deals Burn Damage and inflicts Psychosis.
Ancient Weapon
The Ancient Weapon is a ranged weapon that deals Burn Damage and high damage to structures.
Alien Flare
The 
Alien Flare is a bright and long burning Flare item.
Alien Trinket
The 
Alien Trinket is a minor artifact that deconstructs into an 
Oxygenite Shard
Alien Curio
The 
Alien Curio is a minor artifact that deconstructs into a 
Sulphurite Shard
Alien Ornament
The 
Alien Ornament is a minor artifact that deconstructs into a 
Physicorium Bar
Trivia
- Every generated level in Barotrauma contains an artifact somewhere, even if only laying on the cavern floors. This implies their creators must have been incredibly prevalent in this section of Europa.
- A Moloch is sometimes found instead of an artifact at the end of salvage missions in the quest "Salvaging an artifact", as they emit the same kind of infrasonic signals. Killing the misleading creature will still be considered a success.
- As of Version 0.8.2.0, items taken from the ruins in Campaign mode will now be present in the next round. Previously, these items were deleted after ending the round.
- Since the Thermal Artifact is only active when inside a submarine's hull, it suggests that the Thermal Artifacts were likely used by it's creators to defend their territory.
- As ruin walls use the same internal file structure as submarine walls, most third party anti-griefing systems will return a false positive whenever they are damaged. This could be intentional, as it is possible to construct a submarine out of ruin walls in the Submarine Editor.
