Aerial shot of the building.

The apartment building. or simply the building. refers to the apartment building at 2311 North Los Robles Avenue, Pasadena, California. When viewed from the satellite photographics in "The Countdown Reflection " episode it appears to be located at 215 South Madison Avenue. Leonard. Sheldon. and Penny occupy apartments on the fourth floor. Adjacent to a lamp store, it is located about a block from Pasadena City Hall, which is visible through Sheldon and Leonard's window. The building is also located near a Chevron station on Colorado Boulevard, being that Leonard makes the excuse that he uses its bathroom when he and Penny began seeing each other for the second time in season 5.

The apartment building has at least five floors and sixteen apartments (based on the number of mailboxes). The Elevator has been broken for several years, after it was damaged by one of Leonard's experiments involving rocket fuel, as explained in The Staircase Implementation  causing everyone to take The Stairs. The building also contains a laundry room in the basement.

During the initial production of The Big Bang Theory. Chuck Lorre stated that the set department had built him a stairwell with three walls, and he didn't know of what to put on the third wall being that it was the most visible. One of his producers suggested that Chuck Lorre put in a broken elevator, which would add to the reason why the characters had to use the stairs.

The only separate sets built for the apartment building (albeit the apartments) are the lobby (ground floor), the laundry room, and the roof. The stairwell is the same set for all shots, but accessories and details are changed inside the hallway between each shot filmed to create the illusion that the actors are ascending or descending each floor.