The Hidden Basement is a concealed room beneath one of the tenement houses of New Haven.
The Hidden Basement is something that was initially talked about by one of the game's developers when he talked to another player during the Gaming With the Developers event. The developer hinted that there was a "hidden basement in New Haven" and was "inaccessible after a certain point". The majority of the details about the basement, including how to enter it, were known after a user posted and asked about it on the Borderlands official community forum, which in turn led to a discussion that led to the secret being revealed when a user accidentally stumbled upon the entrance.
Entering the hidden basement is only possible during the Another Piece Of The Puzzle mission, where the Rakk Hive is killed. The blue hut can be entered only while the mission is active and will be rendered inaccessible once the Vault key piece is picked up.
The basement usually has 3-5 Bandits, which can be Psychos, Mutant Midget Psychos, or Bruisers, and even a Badass. Objects contained in the basement include a silver and a red weapons chest, and some lockers. One bandit will be standing in front of the elevator (the side where it has no railings), while the rest will emerge from a hidden door in the corner of the room (to the player's right and back if he is on the elevator and facing where the first bandit stands).
Inside the basement there is a vaguely tree-shaped pile of greenish junk decorated with grenades. There is also a macabre version of the leg lamp from the classic movie "A Christmas Story", complete with its own personal shield. Surrounding the 'Christmas tree' are a number of presents, including several chests and two weapon crates, one of which is guaranteed to contain a Gearbox manufactured weapon called the Rider. The red Flavor Text in the Stat Box for this weapon warns, "Careful...you might put someone's eye out." This is another reference to "A Christmas Story", in which Ralphie, the main character, asks for a Red Ryder BB gun for Christmas, only to be told by all the adults he mentions it to that, "You'll shoot your eye out!"
- The blue hut at the back of New Haven is the entrance. It is across the street from the building with the radar dish on top and the entrance itself is a sliding door that will open automatically when a character stands next to it.
- Driving away from the town and using the "lock" function (A on Xbox, X on PS3, spacebar on PC) may lock onto enemies underground.
- The three lockers in the basement have a much higher chance of spawning items such as pistols, COMs, grenade mods and shields (as opposed to the more common money or ammunition) than usual.
- The "boot lamp" in the Hidden Basement is a reference to A Christmas Story. The main character's father is delivered a sultry leg lamp complete with fish net stockings as a "major award".
- The music track heard during the Rakk Hive battle will be playing in the Hidden Basement. If a character is downed and recovered by Second Wind, the player will hear the music change to the track heard in Skag Gully.