Geothermal Caverns

 is the fourteenth level of Tomb Raider (2013).

Overview Spoiler
The Geothermal Caverns form a mass grave for Mathias' victims, and part of the initiation process for the Solarii.

After Lara escapes the collapsing bridge, she enters the cavern where Mathias has brought Sam for sacrifice for the Sun Queen, Himiko. Sam has been bound to a pyre, where Mathias plans to set her alight.

Lara is determined to save Sam but she investigates her surroundings only to find a whole army of Mathias's people whom she knows she cannot go up against alone.

Just as the pyre is about to be lit, Lara jumps out from cover and shoots the man holding the fire torch. Dmitri and Nikolai begin to violently attack Lara, cursing her for killing Vladimir. Mathias calls for them to bring her forth, but not before they strip her of all her weapons.

Mathias continues to light the kindling, but a sudden and fierce gust of water and winds blows the flames out, convincing Mathias that Sam is the chosen one. Lara is guided away toward the Throne room.

As they are crossing a bridge, Lara attempts to knock the men off, but fails. She does manage to retrieve her bow, but finds herself standing in between both men with nowhere to escape. Her last resort is to jump off the bridge into a gruesome pond of decomposing bodies. The Solarii think she doesn't survive the fall but they are still skeptical as you make your way out unseen, but covered in blood and gore.

There are hundreds, if not thousands of corpses in The Pit, this first area of the caverns. It transpires that this area is used to break the minds of new recruits into the Solarii Brotherhood, and they are thrown into the pit for weeks on end with no food or water, and must resort to cannibalism to survive. Lara witnesses a member of the Endurance crew thrown into The Pit, who is quickly killed by the inhabitants (Lara can choose to shoot the crew member to spare him the pain).

Throughout the main cavern are cages in which victims are kept. Lara witnesses the distress and insanity in the people who are held captive. In The Pit, she is stalked by an insane man known as Gollum, who tries to surprise and kill her.

In most locations there is toxic and flammable gas which Lara uses towards her advantage in most puzzles. After escaping the Pit area, Lara finds her friends, Reyes, Jonah and Alex. They are being kept in an upside down helicopter fuselage hanging from the ceiling of the cavern. Soon after blasting it off to allow their escape, the caverns begin to fall apart, revealing lava flowing below. Lara tells the others to escape while she looks for Sam. A chain reaction of explosive gas destroys the caverns.

A passage leads from the caverns into the Solarii fortress and the Throne Room. An epic fight of flames and chaos takes place as you stumble across flaming bridges and buildings, while Mathias' men try to escape.

Through the fighting, Lara picks up a grenade launcher attachment for the assault rifle, which can be used to break through walls.

Trivia

 * One of the "Prisoner" inside The Pit may start to talking about his wife and daughters when Lara is near to him. Later in the game, Lara may found a Relics (2013) in Shipwreck Beach, a train toys with a name Coco, a plush toys with a nametags, "Millie," and a wallet with a woman and a girl standing togethers in front of the planes. The Prisoner's quotes may leads to this types of information.
 * The animations of Lara slowly going out from the bloods pool is the same animations that is done in the movie "The Descent".
 * There is a strange Prisoner that is laughing whenever Lara enters The Pit. Though the Prisoner did not show himself, but gone after a 3rd attemtp on laughing instead.