In 2005, the cast of The Office settled into a nondescript office space in Culver City, California, for a read-through of the pilot episode. When the actors were finished, studio and network executives asked to see the show’s set. You’re sitting in it, they were told.

Therein lies the magic of The Office, which premiered 15 years ago on March 24 and still maintains a fiercely devoted following long after going off the air. The series followed employees at the fictional Dunder Mifflin Paper Company in Scranton, Pennsylvania, and found joy and heartache in life’s small, ordinary moments. In order for that to happen, a hyper-realistic world needed to be built.

Steve Rostine, the show’s set decorator, was given the task of bringing this unremarkable universe to life. “It’s very hard to create these middle-of-the road environments because you don’t want your set to be the star,” Rostine tells AD.

Each year (except during seasons one and four), the set of The Office would be decked out for the Christmas episode. Photo: Paul Drinkwater/NBCU Photo Bank

He bought institutional-looking artwork for the walls and tracked down old desks with matching credenzas from a bank. The problem was, the desks looked a little too nice. Rostine gave them to a carpenter, who roughed them up, then sawed off the edges so they could be crammed together. Dunder Mifflin ended up feeling so much like a real office that visitors would sometimes try to use the bathrooms, which—much to their misfortune—didn’t actually work.

After the first season wrapped, creator/showrunner Greg Daniels moved the set to Chandler Valley Center Studios, a squat gray building in the San Fernando Valley. “He didn’t want the show to be shot on a studio lot with a bunch of other sitcoms,” Matt Flynn, the series’ art director and production designer, recalls. “He didn’t want that sitcom feel to rub off on The Office.”

Ken Kwapis, who directed 13 episodes, including the pilot, adds: “The area where we shot is very scrubby and industrial, and I think the only other film production that went on there was porn. It helped the cast feel like we weren’t making something in a Hollywood studio.”