|This article is non-canon.|
The subject matter of this article does not take place in the "real" Half-Life and Portal universe and is considered non-canon.
Halls3 takes place in a series of connected buildings on the outskirts of City 17. The Citadel can be seen in the distance. There are three main buildings in the map: the red and blue buildings placed on the lower level and the center building containing Health and HEV Chargers on the upper level. Each building is open to a small outer enclosure with a highway along one perimeter.
The red and blue buildings are connected by five separate hallways, each with a teleport that leads directly to a different weapon. The type of ammo located in front of the teleport gives a clue as to what weapon lies on the other side. Raised walkways overlook the interiors of the red and blue buildings.
 Behind the scenes
Halls3 was created by Chris Ashton, co-founder of Turtle Rock Studios, during his time at Valve between 2001 and 2002. However, the map itself was not publicly released in the game until 2013. The level is a remake of one of his earlier Half-Life multiplayer map works from 1998, Halls2, developed while he was a member of Presto Studios. In turn, Halls2 was based on a 1995 netmap made for the game Marathon known as Halls of death, described by Ashton to be one of his favorites.
Hallway with a teleport leading to a shotgun, hinted at by the shotgun ammo.